We've had some very warm weather here in the UK over the past few days and my container tomatoes are wilting - both from the sun above and the hot patio below!
The quickest way to revive a plant that is wilting is to spray it with a mist of water, 'though this is not recommended if the plant is behind glass as it can cause leaf burn.
Another drawback of prolonged periods of warm weather is that the air can become very dry.
This will effect flower pollination as the pollen becomes too dry to transfer successfully from the stamen to the pistil and self-fertilise.
One way to help pollination in these conditions is to wet the floor area where your plants are growing - the patio or greenhouse floor etc. This will produce some humidity, however temporary, and may help the situation.
Some days I have to water twice ... reluctantly. However, It's that exciting time of the season when you can get a good idea just how successful your plants will be - if we get a good summer of course!