Wait until it cools a bit.

My whole tomato growing season is in high heat. I plant in a garden that is fertilized to the specifications my agricultural extension agent prescribes, based on the results of the tests of the soil sample I provide in early spring, then I fertilize again when they tell me I should, a few weeks before my first tomatoes ripen, and again a few weeks after the first ones ripen.

As it works out, I have it adequately fertilized when I plant out, again about a month later, and again after an additional month.

I fertilize regardless of the heat, but I use dry fertilizer and don't water it in, just scatter it around the plants. If I don't fertilize when it's on my calendar, I've forgotten to do it later. If it rains, that means it's cooled down. But I agree that using a liquid fertilizer is probably not good for the tomatoes, nor is using a foliar fertilizer in high heat.

What are the problems encountered with using a liquid fertilizer (say fish emulsion) during the hot months? My
tomatoes in pots are getting watered daily due to the heat,
and could use a small shot of nutrients added....