AHS Heat Zones

[habitat-gardener]

I recently came across the map of AHS (American Horticultural Society) Heat Zones. It explains a lot about why moving 100 miles inland feels like such a different climate, even though it's still in USDA Zone 9b. My Sunset zones have not changed much, either.

Heat zones are defined as number of days above 86F. So my previous gardens were in heat zone 1 or 2 (<1 or 1-7 days). My current gardens are in heat zone 8 (91-120 days -- almost all of July-September and some days in May-October).

Usually, 86F is defined as the temperature at which tomato pollen becomes sticky and new fruits are not formed. The mitigating factor in my climate its that the nights are 20-40F cooler than the days, so the plants (and people) get a chance to cool down overnight.

In my previous climate we got pretty steady afternoon breezes, but in my current climate, we also get gusts of wind in the 20-30mph range, so that it's risky to keep umbrellas up for shade. This week, the temperatures have been good for planting, but the winds have been a bit much. It's fatiguing to work outdoors when there's constant wind! And not helpful for newly planted seedlings to get established.

(The other mitigating factors about moving a hundred miles inland are less traffic, less crowding, and slightly lower cost of living.)

[bower]

I'm only 5 km inland but the microclimate is really different from my mom's place on the coast.
She gets milder temperatures when it comes to overnight lows and frosts, but it gets way hotter here on a sunny day. And we have much colder temperatures in winter and more snow, generally. And the inversion frosts on a clear night.
Wind - well I can commiserate because we are one of the windiest inhabited places on earth. Strange weather is when we don't have any wind... No umbrellas here. Very true that wind will baff you out after a few hours of buffeting. IDKY that is, maybe the sound?

Microclimate is everything where I live because the climate is so marginal to begin with.
I need to get a weather station!

[Julianna]

I loved that map when I lived in the south. I discovered it due to it being on a catalog... Maybe Select Seeds? Grandmother's Garden? One of those types of places... Probable late 90s or early 00s. That thing is fantastic when you move to a hotter place and need to figure out the whole heat versus plantings thing. I never understood why it didn't get more traffic. Cold is only part of the story for most areas!