During spells of hot and dry weather, your trees (including shrubs), will feel it as well as you!
Any trees planted or transplanted within the the last 5 years and all those in containers will need assistance. If any trees/plants show signs of trees, water them. Primarily this assistance is an increase in watering (more each time and more often). Plants will use more water during hot times. I think this is a rare design flaw.
The main way they cool down is by transpiring (sweating like we do), they create a ready brek glow (for those of you who do not remember these ads, it is a surrounding of warmth (in the ads) around kids who had eaten it for breakfast.
So at a time when moisture in the soil / container is usually in short supply,(due to lack of rain); the tree is using/losing it at an increasing rate as the temperature increases, as they try to cool down. When a dry wind is present this is magnified as the ready brek glow is blown away.
With trees/plants in containers, if you can, move them into the shade. If trees/plants are surrounded by hard surfaces, this will increase the effect of heat.