Wow the heat is really beating down today, its probably going to make any heat sensitive plant bolt if they haven't already.  Ive discovered a neat trick though to minimize or at least prolong the switch from vegg. to bloom. Im talking about herbs like cilantro, basil, lettuces and spinach. First of all i keep the plants crowded.  The density of the leaves help shade the root zone, and its the heating of the soil that makes them most likely to bloom.  Daily misting helps, but not so much you drown them.  Harvest from every other plant, leaving neighbors to shade.  Mulch mulch mulch, I got a bunch of leaves from the local cemetery.  And give them a bit of shade, not too much, but remay (shade cloth), or a nice slender tall tree works well.  Lastly, harvest as often as you can even if its just buds and blooms.  Mother Nature and her need to flower is going to win out, but we can scrape as much as possible cant we?