Spudakee and Arkansas Traveler set fruit for me in the heat of the Kansas summer. Jaune Flamme is a machine most seasons. Riesentraube is productive in the heat. The Artisan varieties produce in the heat here. Brandy Boy, Tycoon and Valley Girl hybrids don't seem to mind the heat very much.

Shell 6A

Last year in northeast Texas, I had good luck with Amelia, Celebrity, and Bella Rosa. I was able to set out good size plants on 3-16 and they started producing ripe fruit last week of May and first week of June. It was a good year with no late frost or freezes. I had several other varieties and a total of 20 plants and they all quit setting new fruit when the temps got up around 92-94 degrees. But all the plants were loaded with small tomatoes that continued to grow and ripen into August.

Here in central Texas, I have never found a tomato that will continue to set fruit after June starts. We're talking high 90s every day in the daytime, and above 75F at night. That makes for interesting gardening. The strategy is to plant out as early as possible - my tomatoes went out last week. Certainly, if you can get fruit started in early June, you can still be harvesting in July. There may be more options in North Texas, though plant-out dates will be later.

As Dan said it isn't in the nature of tomatoes to set fruit during periods of high heat and humidity, no matter what variety. The pollen isn't viable, as it turns sticky and tacky. You can read through all kinds of discussions about this over on the Growing Tomatoes forum here.

But basically it is just the nature of tomatoes. So you have to adjust your growing conditions accordingly - early planting, shading, early AM hand pollination, etc. The condition is called "Blossom Drop" and there is a FAQ here all about it. Sure you can get a few exceptions if you happen to get some breaks in the weather but you can't change the nature of tomato plants and the high heat of summer fruit doldrums is something most all of us have to deal with now and then.

Cherry varieties do better than slicers in general.

Dave

From what I've heard, the "heat set" tomatoes may give you another week or two of productivity, but they don't come close to removing the heat sensitivity of tomato fertilization. The unfortunate phrase "heat set" implies that hey, we produce in high heat! Ain't so.

This got me wondering. What is the evolutionary advantage of tomato pollination shutting down when hot? I mean, why do that? If you have a tomato on the vine when it is hot, it will cheerily finish maturing and produce loads of seeds. But the plants will refuse to produce any new tomatoes. You'd think that if the prime goal in life of a tomato plant was producing loads of seeds, shutting down when hot doesn't seem particularly smart. Any evolutionary plant biologists out there?

Kansas Farm Girl, I'm thinking of growing Jaune Flamme how is the taste for you? I'm looking for a tomato that doesn't mind the heat and has a tart (not sweet) flavor.

HD .... IMO Jaune Flamme is intense and fabulous. You've selected a good one.

Shell 6A

Anyone here ever tried Mocross tomatoes? They are supposed to be able to set fruit up to 98 degrees.

I don't know about gardening in humid heat from personal experience, but in semi-arid heat, there are plenty of varieties I've tried that set fruit when the daily highs are fairly consistently between 90 and 116 or so from late June to mid August or so (with night-time lows being 20 to 40 degrees cooler than the daily highs). Making sure the tomatoes have enough potassium can help during periods of heat and drought, but they still need to be heat-tolerant to set fruit at or past 90° F. I've had more fruit during hot periods if I shower my plants when I water them, or use an oscillating sprinkler to water them (as opposed to watering the soil only). That may not be a good idea in a humid area, though.

Some varieties produce about as well in my area during the heat as during other times (e.g. Sweet Orange Cherry and Husky Cherry Red F1), but some heat-tolerant ones still produce better when it's not so hot, or they just don't produce much at all, even if they produce in the heat. Heat-tolerant cherries seem to more common, but there are definitely cherries not very fit for the heat in my garden (e.g. Gardener's Delight, and Texas Wild Cherry; they both do have above-average heat-setting ability in my area, but not very far above average). Texas Wild Cherry might set fruit in Texas during the heat, though—Texans seem to like it; they seem to like Porter, too. Not everything suited to humid heat is suited to dry heat, and vice versa. There are definitely larger tomatoes that can set in the heat, though (e.g. Pruden's Purple).

Early Girl F1 sets fruit in the heat in my area, since you mentioned that one. Sungold F1 is also supposed to be heat-tolerant. I haven't grown it, but a local friend had a plant with fruit on it in the summer.

You might try varieties like Camp Joy, Pruden's Purple, Homestead, Creole, White Tomesol, Dad's Sunset, Amana Orange, Pineapple, Chocolate Pear, Black Plum, Matina, Mountain Princess, Black Cherry, Yellow Pear, Red Pear, Cuostralee, S. Cheesmanii, Sungold F1, Sunsugar F1, Early Girl F1, Sweet Orange Cherry, Husky Cherry Red F1, Lemon Boy F1, and Roma.

If humidity interfering with the pollen is the only problem, you might try parthenocarpic varieties, which don't need to be pollinated. For me, they've set fruit about the same as those that aren't parthenocarpic (parthenocarpic tomatoes don't need pollen to set fruit, but they do need pollen to produce seeds), however, but it's not humid here. Parthenocarpic varieties include such as Oroma, Saucy, Legend, Siletz, Santiam, Sub Arctic Plenty, and Gold Nugget.

Seedless fruits are sometimes a sign of parthenocarpy. I've had some seedless fruits from Black Giant, North Dakota Earliana, Sophie's Choice, and Veni Vidi Vici, and very few seeds in some other varieties like Jackie, and Ovita (1 seed). There might be another cause of seedless fruit there, however. Jackie seems to be heat-tolerant, but it doesn't seem to be a good fit for my area, as far as production goes. I'm not sure that any of the others are particularly heat-tolerant, though, but North Dakota Earliana is supposed to be.

I was very concerned about selecting heat-tolerant plants for 2016, but not as concerned in 2017, and I seemed to have had at least as many heat-tolerant tomatoes in 2017. I think it can make a difference, but with the exception of a few kinds of tomatoes, the way you care for your plants probably makes a bigger difference in the long run as to how much fruit you'll get (whether or not you get it in the heat).

I just wanted to update this thread with some notable heat-tolerant tomatoes (in my area, anyhow), which I grew in 2018: They were Sausage and Brandy Boy (john11840's stabilized version): those were two big standouts (out of about 65 varieties). Cougar Red (from Sand Hill Preservation Center) was also decent, but I'd recommend the first two over those for production per square foot (Cougar Red had a big plant with a lot of foliage). I grew a bunch of commercial F1 hybrids, but I wasn't particularly impressed with any of them, with regard to heat/drought-tolerance, as most of them wilted in the heat and didn't produce much (I'm not sure how much they actually set in the heat, but foliage-wise, Jetsetter F1 and Bush Early Girl II F1 had the healthiest plants; additionally, they did produce the most pounds of fruit among the F1 hybrids).

Out of the repeats, in 2018, I liked Mountain Princess the most.

Normally, the heat wouldn't cause the plants to wilt and such, but we had black plastic down and that made the soil extremely hot. The soil was even too hot for our watermelons and muskmelons. It was a curious year, too. The sun seemed somehow different as to how it affected the plants (including the perennials). That could be because we cut down a bunch of trees (and now we have more sun), but it seems like something else must have happened, too.

I read this thread even tho hasn't been a problem for me here in Pa. But I'm wondering, I read the statement: "The pollen isn't viable, as it turns sticky and tacky. " by Digdirt2. Is it possible that the pollen could be collected and saved till needed later. I know they do that with apples.

Would you recommend the Super Fantastic variety?

I’m in central Florida for a few years now. i had good success with seeds from the Campari tomato, from the market. Set well in heat but succombed to bugs! Trying Jaune Flamme this fall.