It's been really hot here lately, 94 degrees yesterday. From what I understand it's the hottest summer on record since they began keeping track. Should have a little temperature break today and tomorrow though here where I am, the 80's will feel good.
We are having a few issues with lettuce wilt and some of the other plants because of that heat. Probably the oddest is that it looks like the strawberries have been burned slightly. So far, the potatoes, garlic, peas and cucumbers don't seem to be having any heat issues. Kind of surprises me with the potatoes, they are one of the more temperature sensitive plants you can grow.
Make sure you are properly watering your garden and lawn, either water in the evening around sunset or before 7 AM. During the daytime if you water it can kind of be like little lenses on your plants which will in essence burn them. It can also cause plant DNA changes from what I also understand which isn't a good thing.
If you live in a place with higher humidity than we have here, water everything in the morning. Standing water over the evening will cause mildew.
Here in Colorado where I am our normal humidity is between 35 and 40%. That's just about desert dry, you need to water at night or it won't soak in properly. This is what I based the advice I gave in "Growing Things" I'll admit.