What a good question! here in Michigan its around 90 degrees right now so I am worried!  I just planted my spinach and lettuce for fall harvest. the spinach I put in the refrigerater for a couple of weeks. The lettuce just direct sow. I have a shade cloth over them and am watching that they don'y dry out. They are on the eastern side of my house, morning sun. I think using shade cloth has done wonders for protecting tenders from any kind of harsh weather.

     I don't know if I answered a question , lol, but I'll be reading this thread for others' input!

Hi Miss Nellie, most fall veggies can be planted at high temps. The only issue is keeping the seed bed consistently moist to encourage sprouting. If the planting area is in very hot, direct sun, some shading in the afternoon will aid germination. 

Plants that struggle the most to sprout in hot temperatures are lettuces and spinach. You can start these in small dishes and keep them refrigerated. They actually prefer germinating in temps of 45°-55°. As soon as the majority of the seeds germinate, get them into sunlight fast, but by degrees, don''t just remove them from a cold refrigerator and stick them on a hot deck. Keep them watered with ice cubes or ice cold water from the fridge for the next couple of weeks.  For larger plantings this may not be doable so just simply shade and watering with cold water is about the only thing you can do.  

And yes, you can make your own seed tapes and put them in the fridge. I think you're looking for this thread in which I talk about doing this and refrigerating the tapes to trick the seeds into thinking it's spring. These tapes will not sprout or germinate until they are in the ground. If however you make seed mats using paper towels, the paper towels can be wetted down, rolled up and put into ziplock bags, and then refrigerated. These will germinate giving you a jump on that fall garden. Then they'll just need shade and to be kept consistently moist to protect against the heat. (I think this answers your original question.)