Depends upon the tomato var but fruiting stops ~lo 90ºF and metabolism stops 9-12ºF above that, tissue damage generally you need to approach ~110ºF. The good cold-adapted ones knock a few º down. Squash IIRC about the same-ish.

Dan

Regardless of the reaction of tomato/squash, I begin to panic when the thermometer goes above 85º, Kenny.

In the rose greenhouse, we would throw water on everything at that temperature. A misting system was installed while I was there to replace a worker with a crazed look in his eyes and a finger over the end of a hose, running up and down the rows.

S'

Greenhouse Shmeehouse. Forecast of 96º today, about that yesterday, and if you ever wanted to see a bunch of sad, newly-set-out tomato seedlings, look no further than the '52 gardens.

Heavily mulched with grass clippings, well watered, and fingers crossed.

I was pretty sure this weather was coming,, so I got out everything early to get acclimated, but still some ornamentals in ground are unhappy and the lettuce 'Skyphos' is not nearly as heat tolerant as advertised, whereas 'Mottistone' is more so. I'm hoping the 100+ pea pods ripening now don't get cooked in the next couple days.

Brutal heat swings around here lately.

Kenny, you might want to think about investing in whitewash or shade cloth for the GH to cut the light coming in.

Dan

Thanks for the comments every body.
Supposed to get close to 100 tomorrow, Monday.
I will run the water part of the swamp cooler at all time. Cooler is on a thermostat at about 80 degrees.
I think I could be better off with the swamp cooler and GH than the out side garden stuff.
Shade cloth??? I just spent 2 weeks tieing the green house down with steel posts and bailing wire in the wind storms. No way am I going to try to throw a cloth over it.
Maybe I should have placed it under a shade tree.
One thing about a GH, is you learn some thing new every day.
Kenny

Our greenhouse ops class taught it was pretty much standard procedure that shade cloth/whitewash went on after date X and came off after date Y.

Dan

I use a 50% shade cloth on the greenhouse, it knocks off 20ºF in there. I also have one on the NE porch which is a 65% shade sitting on vegas, or horizontal wooden beams 8' off the ground, that dramatically cools the house by shading the west windows.

I don't want to talk about swamp coolers. I've been trying to set mine up for 4 days now, with one thing after another going wrong, currently letting some black goop dry that I hope stops the leak into the house. 72 hour cure time.

Did I mention it's 96º out?

Check out the whitewash Dan mentioned, Kenny. It's been used on commercial greenhouses for decades, and it WON'T blow off!

:-)
Skybird

Followup:
I just ordered a bottle of varishade.
Cheap enough, But the shipping costs a bunch.
So thanks for the comments.
We will see how it works, Kenny