Subject: Re: Climate zone's in US

From: Jennifer Stiller <[email-masked]>
Date: 19 Feb 1995 00:30:25 GMT

In article <[email-masked]> linus, [email-masked] writes:
>Subject: Climate zone's in US
>From: linus, [email-masked]
>Date: 18 Feb 1995 22:29:31 GMT
>>Can anyone explain the climate zone's in the US? How many zone's are 
>there, where are they located and how are they defined? 
>In Europe the climate's are named after area's (mediteranean-, land- 
>or seaclimate etc.).
>I often read interesting things in this newsgroup, but it could be a 
>lot more intersting when would understand what these climate zone's 
>are.
>
>Thanks.
>
>Alexandra van Tongeren ([email-masked])
>
The zone map concept was developed years ago (I don't know how many)
under the direction of the U.S. National Arboretum in Washington DC.  A
map is developed by the U.S. Department of Agriculture and published by
the government.  It shows climate zones for all of North America
(including Canada and Mexico).  The zones are based on "average annual
minimum temperatures" and the current ones are based on the lowest
temperature recorded for each of the years 1974 through 1986 in the U.S.
and Canada and 1971 to 1984 in Mexico.    (The map also covers Hawaii,
even though it is not in North America.)

There are 11 zones shown on the current (1990) version of the map, the
official version of which is a magnificent document printed in color on
heavy paper about 1m x 1.3 m in size.  It is detailed enough that I can
almost figure out whether my garden near Philadelphia is in zone 6 or
zone 7.   To give you an idea of the zones, the temperature range for
Zone 1 is below -45.6 degrees C, zone 2 is -45.6 to -40 degrees, zone 3
is -40 to -34.5 degrees, etc.  My zone 6 is - 23.3 to -17.8 degrees; zone
7 is -17.8 to -12.3 degrees.  Zone 10  (the part of southern Florida that
has temperatures that you imagine Florida has) has an average low
temperature of -1.1 to +4.4 C.  (Zone 11 is in Mexico and a bit of
Hawaii.)

Note that all these temperatures are winter minimums.   The idea is to
let gardeners and farmers know what plants are likely to be winter-killed
by the cold.  The zones do not take into account the enormous variations
in such factors as summer heat, rainfall, and soil type, so they don't
really tell a person what will survive the whole climate, just the winter
cold.

Jennifer Stiller   ([email-masked])