Tomatoes grow well throughout the winter in Florida. By late spring, though, it’s too hot to get the fruit to set. I thought a bit and came up with a solution: frozen water in 2-liter soda bottles.
If I’m having trouble getting the fruit to set as the weather gets warmer, I simply put a plastic tent over the plant at night, and under the plastic tent I place the ice-filled bottles. This setup takes the air temperature down enough to allow the fruit to set on the tomato plants, and it works very well.
Palm Harbor, Florida