Growing zone map & zone temps

[Ktrain]

I was looking at some zone maps and realized that some put me at zone 8a, when most have me 7b.......I'm very close to the border anyway.

So out of curiosity, what map does everyone use?

USDA is probably going to be most accurate I suppose.

https://planthardiness.ars.usda.gov/pages/view-maps

Map for Canada below.


Also I go by Farmers Almanac to see my avg zone temps and elevation.

https://www.almanac.com/gardening/frostdates

[batty]

I like WeatherSpark.com for most of this type of data.. much more detail info on temperatures, precipitation and sun for each month and day, and ability to compare different locations side by side. The average low and high temps are more important for planting timing and planning than frost dates for me. Even well past frost risk it can be too cold for summer plants to grow.

I've never found a last-first frost site I was happy with.. are they counting frost as 32F, 38F? At what probability? Most don't even say, and dates seem to vary a lot.
USDA is the official source for the zones.. though many of their maps are still using averages from 1976-2005, they might be a bit dated.

I broke down and manually calculated this stuff from the last 20 years temp data from my closest weather station.. put me a half zone warmer.

[Ktrain]

Wow thanks, that's good information.
I will have to check out that site.

My parents were big on the Farmers Almanac while I was growing up....so I guess that why I follow it too. (old habits)

Thank you for your response.

[Ktrain]

This is considerably different than the Almanac "growing season" information.

I like this better...lol

[ginamcd]

When I search by zip code, it lists my town as 6a. When I zero in on my actual neighborhood, I'm a stones through over the line into 5b.

In 2012 when I started planting a garden, I believe the US zone map had me in 5a.

Maybe by next year I'll be solidly in 6a...

[Ktrain]

Same here really, The USDA map link I posted above lets you zoom right in on your area, I can take a 40 minute drive south and be in zone 8a, or a 40 minutes north and be in 7a.

Either way....It's a pretty decent growing season.

[don_sanders]

Hooray for global warming. I can’t wait until I’m a solid 8 with beach front property.

[Ktrain]

People in Arizona have been waiting for that...lol

[PacNorWreck]

For those in the west, Sunset zones are really helpful - they take summer high temperatures, seasonal weather patterns, and precipitation into account in addition to winter lows. The result is that anywhere with a given sunset zone designation experiences very similar weather all year and can grow essentially the same palette of plants.

I like it a lot compared to USDA zones, since I’m in a Zone 8b that looks very very different from zone 8b in Georgia.

[oat]

Sunset zone is helpful but doesn't work that well in the Bay Area. For example, all of SF, Oakland, Berkeley, and the bay shoreline are all in zone 17 but because of microclimates even in SF itself, there are 2-3 heat zones.

[PacNorWreck]

oat that makes sense. I imagine the Bay Area could have its very own zone system, the microclimates out there are crazy!!

[Ktrain]

I imagine that whole coast line would be pretty crazy.
So many factors though....the whole zone idea is just a reference point anyway.

There are a few things I wish I could grow here without a bunch of hassle....dragon fruit is one, tried and failed.

[Clarktj2]

With these polar vortexes I can never tell if I’m zone 3 or 7.

[VentSolaire]

One thing to keep in mind if you are using a Canadian map to compare with USDA zones: Canada's plant hardiness zones are based on different factors than the US zones.

Canada’s plant hardiness zones map was originally developed by Agriculture Canada in the 1960s. [...] The hardiness index was ultimately modeled as a function of seven climate variables that influence plant survival and growth: Mean minimum temperature of the coldest month, frost-free period in days, rainfall June through November, mean maximum temperature of the warmest month, rainfall in January, mean maximum snow depth, and maximum wind gust in 30 years.

[...]

The United States Department of Agriculture (USDA) also has a hardiness zone map that is used to guide planting decisions in Canada (planthardiness.ars.usda.gov/PHZMWeb/). It is based solely on annual extreme minimum temperature — the average coldest day of the year — so it does not include the effects of factors like snow cover.

Agriculture Canada produces maps for both models. You just have to be careful and aware of what type you are looking at.

This map is using the seven climate variables (same as in OP): http://planthardiness.gc.ca/images/P...FS_Map_30M.pdf
This map shows locations in Canada using USDA critera: http://planthardiness.gc.ca/images/P...DA_Map_30M.pdf

[VentSolaire]

@Ktrain

The two maps from Canada that I have linked are using data from 1981-2010. I don't know if the USDA have updated versions.

[Ktrain]

I would venture to say they probably do not have updated maps.
Thank you for linking those.

[ginamcd]

The USDA maps for the US were updated within the last ten years. As mentioned above, my zone has changed since 2012. I'm expecting they will update them again soon.

[2AngelsMushrooms]

Another thing to keep in mind is that the USDA revised the growing zone map in 2012. While that was 9 years ago, occasionally I do see websites using the old data for some reason.

[Ktrain]

Yea not sure why it's so difficult to keep it better updated.
Every 9 years or so should be good...lol