I suspect they'll drop. Nighttime temps below 55F make them do that. Though some varieties can tolerate colder temps. If they fertilize, they may produce misshapen fruit.

if they aren't that big yet, put buckets over them, or some type of plastic dome to make a greenhouse. really helps protect them even though 43F won't kill them, just slows growth.. the heat trapped in the soil from the sun during the day will radiate out at night and warm up the dome and keep them warmer than the actual ambient temperature.

keep in mind that while the forecast/temperature might be 43F, it could be 40F or slightly lower since temperatures at ground level can be as much as 5 degrees cooler than where forecast temperature sensors are typically located.

if you do cover them, don't forget to remove it after the sun rises as temperature will rocket quickly inside an enclosed area.

I don't think we're talking about plant survival. They'll do OK down to just above freezing. But cold temperatures are not blossom-friendly.

Yes, blossom drop and/or catfacing could be a result of blooming during cold temps.

How warm are the daytime temperatures?

Mid 70s. I checked the flower buds today and they haven't dropped. The tomato type I'm growing is supposedly resistant to cat facing according to the seed's website.

This site seems to have a lot to say about blossom drop.

That is a great site Shule.

The bottom line for OP’s question has a lot to do with variety when growing at the temperatures she is experiencing. I’ve had those temps on certain nights in my high tunnels and fruit formed perfectly for most varieties. Sure, some may be catfaced but that depends highly on variety. For instance if you are growing cherry/grape varieties you won’t have catfacing on 99.9% of the fruits. Larger heirloom varieties can catface if you sneeze at them.

What wasn’t mentioned is the duration of the lower temps and the other factors mentioned in the UF site. I would not be concerned about high 50s but low 40s for more than a few hours is not good for blossom set.

My general feeling is that if I can stand next to the plant without a coat on for the night they can handle the temps and set fruit. I just never have ever proved that.

But I need to go now cause I’ve thousands of plants, few blooming, that are being hardened off in a greenhouse and although I have a stove cranking out heat in low 40s, the sun is out bright and to complicate things the wind is whipping up to 50 mph.

I think you'll be fine. I've had plenty of nights in the 40s with tomatoes, and didn't have any blossom drop. They might not all fruit, but they didn't fall off. Just my .02

So my flowers didn't drop off when the temperatures were in the 40s, but they will hit 36 in a couple nights. In North Texas (zone 8a), it rarely drops below 40 this late in the year. I am a bit concerned about the flowers now, and I understand that there is a high chance the flowers will drop. The plants are grown in containers on a concrete patio on the south side of a heated building. The containers are a couple inches away from the building, and some heat radiates out. So will 36 be low enough to actually damage the plants or does it have to be freezing.

Also the varieties I'm growing are the Sweet 100 and Ozark Pink.

I get really concerned when temps drop below 40*F and calm (no wind). Frost can form at ground level and then plants are toast. Buildings nearby may help but it’s not a sure thing.

If no frost damage the Sweet 100 cherry may set fruit on half of the blossoms and you won’t notice the difference.

When my temps hit 45F, my open blossoms dropped. My closed blossoms did not.

So I looked at the hourly forecast for Friday night, and it says it will rain in the evening and stop at night, and the temp will be in the 70s. I assume there must be a cold front because the temperature lowers to 40 by the end of the night. I’m hoping that the warm rain will help lock in some heat in the soil because I read that water can lock in heat into the soil.