We're in the middle of a heatwave going on over a month here and I have been trying to seed some clover in patchy spots in the lawn and as a living mulch for a few of my garden beds and it has been pretty shitty trying to keep the soil moist to sprout seeds. I would definitely recommend waiting until it has cooled off and there is regular rain maybe? IDK I don't have a green thumb

I don't wait for rain, but when I see there's going to be a few days of rain, I try to get some seeds out there before it rains. A few days of rain might give the seeds a good start, and then, you could mulch the seedlings to help them make it to the next rainfall. You could use a handheld tool to cut competing plants like grass and use them as mulch. If you can spend a little time every day or week, then you'll figure out what works.