Is it hot where you are? I am in 7b and we are rarely above 100 for more than, oh, 4 days in a summer. If you are looking at heirlooms, etc., watch out for days to maturation. Some of the heirloom ones can be long. I would stick with varieties you know will produce well and quickly in your location, rather than trying something new. I have planted starts of tomatoes in mid-June and had a crop. It was 25 years ago, so I can't remember how BIG a crop, but I remember being happy with it. We don't get frost till mid-November, though.

The high nighttime temperature will affect pollination of the flowers, but not the ripening of the fruit. Most tomatoes won't set fruit when it's consistently humid & hot. Hot sun on your maters will sunburn them. That's no good. And generally hot temps will cause fruit to ripen unevenly, mottled, and quality is not as good as fruit grown in the cooler months here. Sweet 100's and most cherry or currant tomatoes can handle heat much better than larger varieties, so should do alright, with moisture in the root zone, well into the summer. One thing to remember, "full sun" does not mean the same thing here in FL as it does anywhere else. A little filtering shade is best.

Get 'em going. They'll be fine. Hey Norm, do you stake your plants or let them sprawl? I've seen them done both ways but can't remember which is better. Staked is good for me right now as I haven't worked up a proper garden and have mine in the mulch beds. But once I do make a real garden, I was thinking about letting them run across the ground like my uncle used to do. Seems like a lot less work that way. But I may be missing something.

Generally with the cooling weather and lesser sunlight, the tomatoes can be removed from the vines if they are still green. Some folks ripen them on a windowsill and others ripen them with an apple inside a paper bag. The apple as it ripens releases ethylene gas which acts as a ripener to the tomatoes. I doubt that the plant will produce more fruit because of the above mentioned conditions.