I have noticed over the last few weeks how quickly my plants, mostly tomatoes, are drying out in the plastic pots I am using.
I have started sitting the pot inside another pot of the same size.
It has kept the inner pot cool and the soil is not drying out so fast.

In other words, double pots. It does make a difference.

That sounds like a good idea. It's pretty windy round me so things do dry out quickly. When my washing is drying a treat, my plants are drying out too!