[NAFEX] climate zones

Bob Randall YearRoundGardening at comcast.net
Tue Feb 24 15:37:56 EST 2009

Some years ago while trying to advise gardeners and farmers all over  
the Houston area, I became aware of just how bad the existing USDA  
zones were--both out of date and not very helpful, and insensitive to  
local differences (the area has places where there is one frost every  
other year and others where there are 25-40 every winter).  I started  
doing web based research on historical weather in the Houston  
Galveston College Station Metro Region.  What I found was that even  
the weather data is not collected as if people used it for plants.

For example, if you wanted to know how many frosts to expect in a  
winter--suppose you want to grow a lemon or protect your peppers for  
example--you can't find this out easily since the weather data is  
collected and reported by calendar year.  It is actually necessary to  
manually count up all fall winter and spring dates for the last part  
of one year and second part of another to get a total, and then do it  
for that location for the last ten or 20 years

As anyone with math training knows, averages (mean or median??) tell  
you very little about the extremes or their frequency, and plants care  
mostly about that.  So I decided to report frequencies, rather than  

So what I did was a lot of mind numbing counting on NOAA web sites.  
But the way of reporting is much more useful if you grow fruits or  

See http://www.urbanharvest.org/advice/basics/weather_data.html

This is for our area, but there is no reason why similar effort  
wouldn't work anywhere.

Bob Randall
On Feb 21, 2009, at 3:01 PM, Michele Stanton wrote:

> The USDA climate zones are not meant as an all-encompassing guide to  
> what grows where.  They are based on average winter minimum  
> temperatures, and nothing more.   Their main advantage is that they  
> are so widely used.  You can find similar maps for almost any  
> country or area in the world now. Read more at: http://www.usna.usda.gov/Hardzone/index.html
> Those of you West of the Rockies should look at the Sunset climate  
> zones.  They're a much more accurate picture of climates.  I  
> introduce students to Sunset's national maps even though I live in  
> the Midwest. I wish they were more widely used.  They're based on a  
> larger number of factors, such as minimum and maximum temperatures,  
> rainfall amount and timing, humidity, and length of the growing  
> season. Check them out at:  http://www.sunset.com/garden/climate-zones/
> Some nurseries use a combination of USDA zones and AHS heat zones,  
> which is at least a little more helpful.  If you haven't used the  
> AHS heat zones, you can obtain info for your area by entering your  
> zip code.
> http://www.ahs.org/publications/heat_zone_map.htm
> Michele in SW Ohio
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"Share What You Grow and What You Know!"

Bob Randall, Ph.D.
YearRoundGardening at comcast.net

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