Also check and fill your wiper fluid reservoir. A summertime thunderstorm isn't the best time to run out of wiper fluid or to discover your blades aren't performing properly. Check the battery. A battery gives little warning before it goes dead. And it'll likely do so when you least expect it.
Hot weather can put additional strain on a battery similar to what is experienced in cold weather.
If your vehicle battery is more than three years old, have it tested at a certified automotive repair facility. Also, make sure the posts and connections are free of corrosion. If you're embarking on a long trip, consider replacing the battery if you don't know how old it is. These days, batteries are not very expensive, and it's cheap insurance when you're out on the open road. We also recommend that you always carry jumper cables, as mentioned below in the emergency kit section.