Talk:Humid continental climate

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[edit] Subarctic or Humid Continental if summer lasts 3 and a half month?

The article about subarctic climate says 90 days frost freee periode at most and no more than 3 months of summer (mean 24-hr average at least 10°C). However, this article says that an area with summer lasting less than four months (and winter colder than -3) has a subarctic climate. A substantial area in Scandinavia, Russia and Canada have summers lasting more than 3 months and less than 4 months. Lillehammer, Norway, has a summer lasting on average 108 days, frost free periode is a bit longer, while winter (average below freezing) lasts 5 months, with January average -9 C. So is this a humid continental (Dfb) climate or subarctic (Dfc) climate?

It is based on the monthly average of calendar months, so such is averaged out. It all depends on how everything averages out. CrazyC83 00:52, 26 October 2006 (UTC)
Ok, but for research purposes more precision is needed, and it seems as the line often is drawn at 100 days of summer. Orcaborealis 11:28, 26 October 2006 (UTC)


[edit] Charleston, WV & Roanoke, VA

Can anyone prove that Charleston and Roanoke is is in the Humid Continental climate zone? Those cities do have mountains, but they are not high enough to make a huge difference. The coldest areas of West Virginia and Virginia are in the Allegheny Mountain range. Neither city is located in that area. The Punk 08:50, 30 November 2006 (UTC)

They're much colder than, say Charlottesville, Virginia. Well, I actually grew up in Staunton, VA and then lived in Charlottesville (40 miles to the east on the other side of the Blue Ridge) as a young adult and, subjectively at least, I can tell you that crossing the Blue Ridge makes a huge difference with regard to the climate. In the upper-elevation parts of the Shenandoah Valley, the weather is not that much warmer than it is where I live now (near Kingston, New York, 90 miles north of NYC). Average daytime January highs are in the lows-30s F. In Charlottesville (on the western edge of the Piedmont) most winters are mild, with average January daytime highs being in the mid-40s F. While neither are that high in elevation, both Charleston and Roanoke should be considered continental, since their climates are cut off by mountains from warming southern air masses. Furthermore, Roanoke is a frost pocket below several high mountain ranges. User:bigfun 29 March 2007

[edit] Warm or Hot summers?

In the Köppen article, the Dfa /Dwa/Dsa subtype is referred to as having a hot summer, while the Dfb subtype (hemiboreal) is referred to as having a warm summer. Orcaborealis 09:07, 5 January 2007 (UTC)

Best term is Hot Summer for Dfa and Dwa (>=22°C), and Warm Summer for Dfb and Dwb (<22°C). Since most places in the latter category still get into the low to mid-20s°C (70s°F) in July (January) on average with frequent hot days, calling it a "cool summer" is really pushing things. Most places with cool summers and away from oceans fall in the subarctic climate. BTW, Dsa and Dsb are not humid continental, they are high-altitude Mediterranean as they are only found in higher elevation areas adjacent to Csa/Csb climates. CrazyC83 01:46, 6 February 2007 (UTC)

How about going with 'very warm' (but not Hot summer) for the Dfa, I mean large swaths of Africa, Arabia, Indian sub-continent and other parts of the world have many months with a summer average of over 30°C, that is truly hot. I would agree that below 22°C should not be classified as a cool summer but a warm one at the very least (or maybe luke-warm!!).

I would suggest 'Hot' summer for Dfa, and 'Very Hot' for the warmest areas on the globe, such as Somalia, Sudan, Saudi Arabia etc. Dfb would then be 'Warm' and Dfc 'Cool' summer. Orcaborealis 19:50, 2 March 2007 (UTC)

No -- Dfb suggests a long (three months or so, which is enough for some agriculture), but not 'hot' summer, one with four or more months of average temperatures above 10°C, but none at or above 22°C. Such allows a significant frost-free season suitable for such crops as potatoes and the hardier varieties of wheat. Dfa indicates a month with an average temperature at or above 22°C... and implies a long summer because the transition from a snowy 0°C month takes time through some 'cool' months that may be considered 'spring' or 'fall'(typically May and September -- which implies a five-month summer by climatic, if not cultural, standards). Such crops as maize and tomatoes possible in a Dfa climate with its long summer are impossible in a Dfb climate that has the possibility of a killing frost during much of the year. Dfc climates, in contrast to Dfb climates, have short summers unsuited to effective agriculture. Short summers might allow some spikes of temperature (a 37°C record in Fort Yukon, Alaska north of the Arctic Circle) -- but those temperatures are short-lived. More characteristic is the possibility of a severe frost even in July.

As a rule, summers become warmer and longer as one goes southward through the layers of D climates. Dfa climates are subject to harsh summer heat waves -- but unlike the neighboring Cfa climates to their south they can have weeks of snow cover that allow more intense and more sustained chill than is characteristic of Cfa climates to the south.

Winters that might be long and severe toward the tundra/boreal forest divide near the Dfc/ET divide become shorter and less distinct until the Cfa/Dfa divide near Philadelphia or St. Louis, where snow is possible only as a short-term phenomenon. To be sure, a place like Memphis, Tennessee or Richmond, Virginia clearly to the south of the Dfa/Cfa divide has a well-marked winter unsuited to rapid crop growth in the short, chilly winter. Hard frosts are possible -- and so is snow -- in the more poleward areas of Cfa climate. But we should be discussing that in a Cfa classification. Around the Dfa/Cfa divide one might find that a climatic summer begins in April and ends in October.

The issue is not what is culturally understood as "summer" or "winter"; the words apply to essentially the same months in New Orleans and San Francisco -- and even Honolulu! -- as they do in Edmonton because of shared language and culture, even if "summer" and "winter" have different local meanings in climate; the Köppen classification allows the physical distinctions between groups of climates. --Paul from Michigan 14:51, 2 October 2007 (UTC)

Actually, Dfb is usually defined - and is so in the Koppen classification - by having at least four months at or above 10°C...although some institutions (National Geographic, I believe) use "more than three months" for Dfb/humid continental. I still believe "warm" is correct for Dfb, "hot" for Dfa and "cool" for Dfc. Orcaborealis 19:25, 2 October 2007 (UTC)
Additionally, the article about Subarctic climate says that no more than three months (but at least one) have average temperature of at least 10°C, so a location with three month summer is considered being in the subarctic, and not having a humid continental climate - even if three month of summer, as you mention, does allow some agriculture (depending on soil). Orcaborealis 19:31, 2 October 2007 (UTC)

[edit] Tokyo, Japan Humid Continental??

To me it seems inaccurate that Tokyo, Japan be labelled as a Humid Continental Climate. If you look at the climate chart both for summer temperatures and winter temperatures (as well as absolute minimum lows), this clearly falls into the Humid Subtropical Category and not the Humid Continental Category. Deneb1978 06:04, 1 February 2007 (UTC)

Most of Honshu is humid subtropical, except at the higher elevations. CrazyC83 01:42, 6 February 2007 (UTC)

[edit] Map

The map attached to this article is confusing. It has no legend and seems to have little relation to the two subtypes described in the article text. BobDively 18:59, 2 March 2007 (UTC)

I agree, because on the map, in the midwest, the dark blue (likely the definite areas) extends down to Arkansas, which has a very mild climate. Also, in the Mid Atlantic, there is a very sharp cutoff on the map along the Mason Dixon line. Washington and Baltimore absolutely have a more continental climate than Asheville, Nashville, and Little Rock. The map needs to reflect what is written in the article. Faz90 22:11, 17 May 2007 (UTC)

It should be noted that the National Oceanic and Atmospheric Administration classifies Maryland as part of the Northeast, giving it a humid continental climate [1]

The U.S. Department of Energy lists the continental climate as extending "from Maryland to Maine," and shows a map where the humid subtropical climate clearly ends in Virginia [2]

The National Climatic Data Center also classifies Maryland as having a humid continental climate. [3]

States don't generally fall into one climate zone, at least not in most cases. Western Maryland and Virginia have many places where the annual average minimum temperature is below 45 degrees, which is the threshold for continental. But Baltimore, Richmond, and Washington DC all have annual minimums above 45 degrees, which puts them technically in the humid subtropical zone. Little Rock is right on the line, with an annual minimum of 46 degrees. Strongbad1982 16:41, 2 October 2007 (UTC)

Nanaszczebrzeszyn 04:00, 1 October 2007 (UTC)Nanaszczbrzeszyn

Wouldn't it be better to go with what climatologists have said, though, rather than simply using our own judgements?

Nanaszczebrzeszyn 20:46, 2 October 2007 (UTC)Nanaszczebrzeszyn

Exactly. The facts above place central and eastern Maryland in the Humid subtropical zone. This is verified many times over in other articles on wikipedia, and in the average temperature information on the weather channel. Wikipedia is not the place for original research.

Strongbad1982 20:54, 2 October 2007 (UTC)

More of Maryland should be shaded, and no part of Oklahoma or Arkansas should be blue, let alone dark blue. According to this map, Tulsa has a humid continental climate, although its average temperature in January is 36 [4].72.81.251.212 (JScott06) 21:09, 2 October 2007 (UTC)

Once again, that is not the definition of a Humid continental climate. The minimum ANNUAL temperature must be greater than 45 degrees. A borderline area (shaded in light blue) has an annual minimum temperature between 45 degrees and 48 degrees. Central maryland, including Baltimore, Annapolis, Bowie, and Washington DC have annual minimums ABOVE 50 DEGREES and therefore should not be in the light blur OR dark blue shaded areas at all. They are Humid subtropical in nature. Tulsa has an annual minimum of 47 degrees, which puts it in the light blue shaded area.

Taking the original image and putting it in paint to extend the light blur shaded area is both a violation of original research standard and copyright law. I have reported this to an admin so this image will be deleted if it is not taken down.

Strongbad1982 21:35, 2 October 2007 (UTC)

Britannica Encyclopedia lists the average July temperature for Western Maryland as 65F, and the average July temperature for allegedly "subtropical" eastern and Southern Maryland as 75F. [5] Ostensibly, their sources are a bit more credible than the opinion of some random contributor.

Oh, and if you delete the image I'll just create it again. The map is wrong and I'm making it more accurate. I mean, it's remarkable how the humide continental line cuts off right at the Maryland border. Wow. I wonder how that happened?

Nanaszczebrzeszyn 21:49, 2 October 2007 (UTC)Nanaszczebrzeszyn

And once again, the ability to communicate has broken down. You're quoting July temperatures to justify central MD being continental rather than subtropical. Point is, the DEFINITION of Humid Subtropical climate is a climate in which the ANNUAL average MINIMUM temperature is higher than 48 degrees farenheit. That's the average low for the ENTIRE YEAR, NOT JULY. Baltimore's average annual minimum is 51 degrees, as seen in the article on Baltimore. Subtropical vs. continental is a matter of WINTER minima more than summer temperatures. It makes a HUG difference because subtropical plants, like southern live oak, dwarf palmetto and kudzu need higher winter temperatures to grow, and these plants appear in central and eastern MD but not in western MD.

As for the Maryland border, it is not my fault that winter minima are above 48 degrees in Westminster, MD, Towson, MD and Aberdeen, MD but are below 48 degrees in York, PA, Chambersburg, PA, and Lancaster, PA. Those are just facts.

Strongbad1982 23:00, 2 October 2007 (UTC)

Where are you getting your definitions from? The Koppen climate article states that subtropical is defined by a coldest month average greater than -3°C, or 0 in the United States; the annual minimum is not involved (other sites confirm this[6][7]). All of those cities certainly have winter minima below 48. Take Columbia for example in central Maryland. Using data from weather.com, its average temperature in January is 31.5, putting it just inside the humid continental zone. Even using your definition, it's continental because its annual low is 42. I agree that southern and eastern Maryland, as well as Baltimore city due to urban heating, are subtropical but most of the central portion is continental. Also, your distribution map for southern live oak is wildly different from the one given by efloras.org[8], and is also at odds with what is written in the article. And personally, I have never seen one of these here in Maryland. Hell, I never even see them when I visit relatives in southern Virginia. Check your facts.JScott06 15:29, 3 October 2007 (UTC)

The live oak map shown in the article is the "adaptable range." The map shown in the link is "native range." The difference between the two is that the native range is where the plant naturally occurs, and the adaptable range is the maximum geographic area the plant can be grown in. Live oaks can only survive temperatures down to -5° F before being killed, so they are rated USDA zone 7. While theym only naturally occur in the coastal areas of the Southeast, they can be cultivated as ornamentals in a larger area of the country (although I agree it is rare to see many outside of their native range).

Strongbad1982 16:27, 3 October 2007 (UTC)


The link given above does show that humid continental climates have the coldest month with an average temperature under 0° C (or 32° F). And yes, the Celsius needs to be give first, with the Fahrenheit in parenthesis, because this is a U.S.-centric issue and this article needs to be brought into compliance. Which is why the map needs to be deleted all together. It is only of the U.S. and creates a U.S.-centric tone to the article. That being said, if the map was to stay, the western half of MD would be shaded blue because cities like Columbia, Frederick, and Hagerstown have avg temps below 32 in their coldest month. but Baltimore, Annapolis, Washington DC, Salisbury, etc in the eastern half of Maryland are not. Which means, IMHO, that both maps are wrong. In any case, there should not be a map. the article does a perfectly good and encyclopedic job of defining the areas.

164.92.81.196 16:38, 3 October 2007 (UTC)

[edit] Incorrect claims in article

The article says: "Average annual temperature below 8°C". Where does this definition come from? And, the article says that annual amplitude (monthly averages) is no more than 22°C . This is wrong. The amplitude can be significantly greater. Here is data for Moscow, with an amplitude of nearly 29°C. Orcaborealis 17:51, 3 October 2007 (UTC)
Novosibirsk in Russia has an amplitude of 33 C. Montreal in Canada has a range of 31°C. Orcaborealis 20:48, 5 October 2007 (UTC)

Moscow has five months with average temperatures above 10°C, which implies a "long" summer, but no month with an average temperature above 22°C, which with appropriate precipitation implies a climate in the Dfb group. The May and September temperatures are barely warm enough to be considered "summer" months by Köppen's classification...but it's enough.--Paul from Michigan 23:26, 7 October 2007 (UTC)

Here's another incorrect claim: Nashville and Louisville in the transition zone. Both cities have coldest month averages above 0°C, so they are are in the subtropical zone. [9] [10] Faz90 (talk) 05:37, 31 January 2008 (UTC)

[edit] Boston as Humid Continental climate? - Not exactly.

The mean temperature in Boston in January, the coldest month isn't bellow -3°C. It's only -2.6°C. So, Boston can't be considered as an exact Dfa climate, but as a Cfa climate in which the mean temperature is between the freezing point (0°C) and -3ºC, just like New York. —Preceding unsigned comment added by 189.20.72.66 (talk) 22:24, 4 October 2007 (UTC)

You're right. Actually, the coldest month is -1.5C. Philadelphia is a true subtropical, proven here: http://www.idcide.com/weather/pa/philadelphia.htm. Oh, and by the way, we should call all parts of New Jersey (besides the northwestern part), Boston, NYC, and extreme southeastern New York humid subtropical. If Cape Cod's climate is like the west coast, then it's marine west coast. How come nobody seems to get that? Koppen's boundaries shouldn't change because something on the east coast would then be called "Marine 'West' Coast." Press olive, win oil (talk) 20:44, 4 April 2008 (UTC)

The general consensus among climatologists is that cities in between the 0°C line and the -3°C line are the transition between Cfa and Dfa. This also includes Philadelphia, Frederick (western Maryland), Roanoke (western VA), Asheville (western NC) and Nashville, TN. Cities to the south of both lines are true Cfa Humid subtropical cities, to the north of the line are true Dfa cities. Boston and New York are in between, in the marginally continental zone.

Strongbad1982 22:51, 4 October 2007 (UTC)

The coldest month in January in Nashville is January, with an average temperature of 3°C. That is on the warm side of the C/D line. Sure, Nashville has a real winter -- but the Köppen classification (whichever coldest-month temperature one chooses, -3°C or 0°C, Nashville is Cfa. That's not to say that Nashville isn't subject to hard frosts and blizzards; it just gets fewer of them than places with D winters. Winters are too warm to allow an extended period of snow cover long enough to contribute to a polar air mass, which Köppen originally used the -3°C coldest-month isotherm to separate. St. Louis, Missouri just south of the -3°C January isotherm can get snow, but it doesn't have it for long. Chicago, clearly to the north of the -3°C January isotherm, can get a protracted snow cover that contributes to polar air masses. This applies also to Asheville, North Carolina.

It's essential to understand Köppen's rationale for drawing his lines where he did. He seems to have considered agricultural potential to decide where to draw the line. This may be my experience, but the C/D line seems to separate places where three crops can be grown in two years (let us say northeastern Arkansas) from those where such is impossible (central Illinois). To be sure, the "winter" crop must be hardy near the northern fringe of such a 3-crop, 2-year zone... but November and March are potential growing seasons in northern Arkansas, but not central Illinois. Even the chilly winter months have enough warm days to promote plant growth.

0°C may be the freezing point of water, but a day that has a high temperature above 0°C will lose some snow to melting if any sunlight is available. Just because the temperature at night is below 0°C does not mean that snow will re-form. But -- an air mass over a snowfield will get progressively colder over time. If it is not warm enough for at least some melting of snow, then the air mass will continue to chill. Snow is one of the most reflective surfaces known, and any place with wet winters and average temperatures below -3°C is likely to have long periods of snow cover. Such is Chicago in winter -- not Indianapolis, and not Nashville.

Don't expect Nashville to look tropical; it's much too chilly for palm trees. Calling a place like Nashville, Dallas, or Philadelphia "subtropical" suggests that one might expect thriving citrus industries (forget it!), palm trees (likewise) and no winter snowstorms. But there's a clear distinction between a snowy forest climate in Buffalo and a forest climate in Atlanta that gets far less snow.

Change of direction: what do we think of urban heat island effects? In a marginal area, the heat island effect may warm the climate of a city enough to alter its classification from Dfa to Cfa (St. Louis?) or from Dfb to Dfa (Minneapolis?). --Paul from Michigan 05:01, 8 October 2007 (UTC)

[edit] No Dfb in the Southern Hemisphere?

D climates are rare in the Southern Hemisphere for the simple reason that all landmasses south of between 30°S and 60°S are exposed to the moderating effects of open ocean or are dry enough (Patagonia) due to rain-shadow effects that if they have a chilly month to have BSk (cool steppe) or BSk (cool desert) climates. Temperature ranges are generally slight between the zones of subtropical desert and the Antarctic icecap. Thus the transition in the southern hemisphere between the warm temperate zone and the subantarctic regions is ordinarily Cfa→Cfb→Cfc→ET from north to south, Cfc climates appearing where summers are short but no month has an average temperature below 0°C.

Rare, of course, does not mean non-existent. Some highland areas in New Zealand have one month below 0°C... it's in fact an area with ski resorts. It covers little area, but it exists. It has a Dfb or Dfc climate. —Preceding unsigned comment added by Paul from Michigan (talk • contribs) 22:22, 22 January 2008 (UTC)

[edit] Topeka

Topeka is in the transition zone, proven here: http://www.idcide.com/weather/ks/topeka.htm. I would consider it humid subtropical because Koppen did. Press olive, win oil (talk) 21:35, 11 April 2008 (UTC)

[edit] Juneau

Is Juneau's climate subarctic or humid continental? According to http://www.idcide.com/weather/ak/juneau.htm, Juneau has 3 months that average above 10C/50F and 8 months below this line. However, 1 month is on that borderline. I read that Juneau was the size of Rhode Island on the internet, so the subarctic-continental border would be located in Juneau. However, every map that I've come across says that Juneau is subarctic. Then again, many also use 0C as the subtropical-continental dividing line instead of -3C. NYC is considered humid subtropical by Koppen standards. Press olive, win oil (talk) 22:32, 13 April 2008 (UTC)

Because the summer temperatures are not very high in Juneau, I believe it would fall under the Marine west coast climate instead, Cfb, or possibly Cfc. Strongbad1982 (talk) 14:55, 15 April 2008 (UTC)

Well, actually the winter temperatures in Juneau are under 26.6F/-3C as proven by idcide. If you look at idcide, the border Juneau is on is Dfb/Dfc. Juneau's winters are a bit too cold. —Preceding unsigned comment added by Press olive, win oil (talk • contribs) 13:18, 18 April 2008 (UTC)

[edit] Cape Cod

Cape Cod and nearby islands get me sick climate wise. Climate wise means I would love to go to Cape Cod in summer but Cape Cod is the reason why some people draw the borderline at 0C. If Cape Cod's climate is like the west coast, call it Marine West Coast. Are San Francisco and Los Angeles on the Mediterranean? I don't think so. However, these places in California have a Mediterranean climate. Also, how about global warming? At the start of the industrial revolution, temperatures were a bit cooler. NYC was between 0C and -3C even then, but climate does change. If global warming continued until it was 20C higher, Maine would have a humid subtropical climate, and NYC would have a tropical rain forest climate. There'd be major differences. Press olive, win oil (talk) 13:29, 18 April 2008 (UTC) http://www.idcide.com/weather/md/oakland.htm says that this random place called Oakland, Maryland's coldest month averages between 26.6F/-3C and 32F/0C. Its hottest month averages under 71.6F/22C It's funny how no one talks about Western Maryland having a Dfb or Cfb climate. It is debatable like Cape Cod. I think it should be considered Marine West Coast and by Koppen's classification, it would be. Press olive, win oil (talk) 19:15, 18 April 2008 (UTC)