We know that including ones USDA zone in personal profiles is almost routine. When somebody is seeking advice has to describe his SUMMER growing conditions too beyond that number. For this purpose USDA zone numbers offer NO or very little help. Here come a useful, practical zoning concept called: HEAT ZONE. from this zoning number one can predict what you can and cannot grow in your HZ. with some degree of success/failure .
Just take my case as example. I am in USDA zone 7b/8a, so are a lot of folks down south from Atl, GA to Dallas, TX. But my heat zone here is ONE( the lonely number) theirs is 7, 8, 9.

USDA zone only can be used to determine First and Last frost dates when it comes to gardening. And whatever happens between those dates has nothing to do with those zone number.

So the next time, you are asking for help, state your HEAT ZONE number too. You might be better helped. Still better yet, include it in your public profile that automatically appears when you write a post.

Yes, mine is HZ 7, the same as my Gardening Zone number. That is true - same or almost the same number - for much of the country.

But yes, generations of us were able to successfully garden long before the AHS Heat Zone map was published in 1995. :)

The number of days over 86 - what the HZ map measures - is very helpful to know for those of you on the coasts or in mountainous areas where it can really have an impact on the crops you can grow and the length of your growing season. Good info for new gardeners too or for those moving to a new location where their gardening will have to change greatly. But for the rest of us old gardeners we pretty much know what our summers will be like from living with them for years.

Personally I find the Sunset zones to be more helpful in the details provided. But all of the zone guides are just that - guides. Not to mention the other zone maps are free to the public while the HZ map was published primarily for for-profit sales ($10) by the AHS.

Dave

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Very good. But it is mostly coincidental that your USDA and AHS Heat Zone numbers are the same. The two zoning numbers are based on different concept.
I am sure that people have farmed and gardened for millenniums but by taking advantage of science and technology we have come a long way in improving productivity, and fighting the elements unfavorable to us.
I am also talking about interacting here in gardening forums. You can help me more effectively if you know my Heat Zone, for example.
Whatever it is, I certainly believe that it is more meaningful than USDA zone numbers when it comes to vegetables gardening ((not talking about trees, shrubs etc).

below is a link that you can go to and figure out your HEAT ZONE number. IT IS FREE ! JUST ENTER YOUR ZIP CODE.

Actually, I remember that. About 3 years after I moved from 8 to 2 my own heat tolerance dropped, a lot.

Update: Wait a second, is that supposed to be days per year above 86F? I am definitely above 7. It would guess 2-8 weeks, depending on the year.

Maybe next week I'll write a little script to run over the Weather Underground data and get my true count.

As far as I know HEAT ZONE zoning is base on NUMER OF DAYS (in which temperatures reach or exceed 86F). That is why it can change drastically as you move further inland from coastal areas. The large bodies of water (seas, oceans, lakes ...) prevent big fluctuation by absorbing and releasing heat.

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Yeah. Heat zone 3 can be hot too but only a for short time; (8 to 14 days over 85F) It can even go to 100F. But statistically it won't be longer than 2 weeks during the whole summer.

I think your HZ is near PERFECT for gardening.

Johns coastal patio: You're in SoCal on the coast, correct? There is no way in hell that you have even close to 4 weeks(28 days) of >86 temps. This year you might get close because of these SPRING Santa Anas, but I'd say it's closer to 2 weeks, at most, in normal years.

I've lived in San Diego all my life(50 years) and the only time(except for the odd year like this year) it gets mid 80's(or above) on the coast is during the October(or so) Santa Anas.

So figure it out. 3-4 Santa Anas per year in the early fall, at max. 3-4 days of heat each one.

I agree about 20 miles inland though. Totally different climate than ON the coast. Been dealing with the heat of the valleys almost my whole life..

Kevin