
Hydration:
You will need more water to drink in the hot weather. Sweating leads to fluid loss that will need to be replaced. If you are accustomed to drinking two gallons of water per day when the weather is moderate, plan on needing at least three gallons for summer survival when things heat up.
Never drink standing water without first treating it. Water from a clear, fast moving stream is generally good to drink depending on your location. However, you do not want to be drinking straight downstream from a town where pollutants are seeping into your water supply. When in doubt treat it no matter how clear it looks.
Treat water with water purification tablets, boiling, or running it through a filter. And fill your water bottles as often as possible. See survival water for more information.
We should mention here too the importance of salt in your summer survival diet. It is almost as important as water since when you sweat you lose both salt and water. Your muscles need salt to function properly. Without it your muscles will cramp, potentially to the point of making them ineffective.
Weather:
One of the biggest dangers to your summer survival is weather. You can monitor weather by paying attention to animals and wind patterns. Birds fly lower when a storm is approaching; and cows will often lay down. Also, take note of the prevailing wind direction. Winds that are frequently shifting are a sign of turbulence in the atmosphere. This is a good indication that a storm may soon develop. Generally the wind will pick up and blow toward a depression (or storm system). It is literally being suck into the lower pressure that is a summer storm. When a storm strikes never use trees for shelter. Always look for caves or rocky outcroppings. If you cannot find shelter it is better to be in the open than under a tree. Crouch down and make yourself into as small a target as possible until the lightning passes.
If you are in a part of the country prone to flash flooding you need to get to high ground as soon as you can. The danger of flash flooding is nearly always underestimated. It can be dry where you are but raining torrents upstream which can cause a 15 foot wall of water to move close to 60 mph to fill the peaceful riverbed you are walking down with tons of water. Always be on the lookout for fast escape routes out of a valley. If you hear a freight train coming down the river, move quickly to high ground.
Exposure:
No matter how hot you get you should leave your shirt on and minimize your skins exposure to the summer sun. You do not want to expose yourself to sun damage unnecessarily. Your skin is your biggest organ. Damaging it can bring fever and exposure yourself to infection. Try to travel at dusk and dawn if it is excessively hot during the day and stay in the shade while the sun is at its highest. Traveling at night can be just as hazardous, but for a different reason; low visibility.
Stay as dry as you can and do everything you can to keep your feet dry rotating socks early and often in the summer. When your feet stay wet for 12 hours or more skin degradation can set in and greatly lessen your ability to walk.
Good sturdy shoes will protect your feet from excessive exposure which can set you up for injuries and deadly infections. If you lose your ability to walk, you are likely not going to survive. Most shoes are not made for long term survival situations. If you lose a shoe or they fall apart coat the bottom of your feet with tree sap and stick birch bark to the sap. This will keep your feet protected until you can get shoes.

Calories: A good source of summer survival food is berries. Wild strawberries, blueberries and raspberries look and taste just like the domestic varieties, just better. There are no berries in the United States that look like a strawberry, blueberry or raspberry that can make you sick with one bite. If you try a berry and it does not taste right, just spit it out. Check out survival food for more info.
Remember to always keep your survival mind. Summer survival can be more about attitude and ability to deal with stress than skills. Many people who are highly trained in survival skills crack under pressure and die because they do not use their skills. There have also been many people with little to no survival training who have made it out of impossible situations. The most important thing is to keep moving forward and keep believing that you can make it.