In the summer, the heat is your car's worst enemy. The extreme heat we've been having can leave you stranded. There are some things you can do to keep your car in running condition even in this heat.
The two most vulnerable points of your care are the battery and the cooling system.
The heat can dry up fluids so check them often and top them off as needed. In the battery, the water and sulfuric acid can evaporate, which damages the battery's internal connectivity. Even a low 90ºF outside can be 140ºF or more in the engine compartment of your car. And it gets hotter when the air conditioner is running. At 104ºF, your car's battery is reduced by half. Test and replace weak batteries and keep the fluid levels checked. Hot weather also corrodes the battery terminals, so check frequently for corrosion build-up and keep the terminals clean.
If the temperature gauge rises, especially in stalled traffic, turn off the air conditioner, roll down the windows, and turn on the heater to siphon heat from the engine area. If possible shelter in the shade of a larger vehicle, a building, trees.
Park in the shade or where shade will be soon, even if you have to walk extra far. Oklahomans and Texans already know this and seek shade over proximity in killer heat.
Interior temperatures of cars with the windows rolled up can rise as much as 25ºF in 15 minutes. Never leave pets, children, sleeping people, or the elderly in a car - even for 5 minutes. It could be fatal.
Check windshield wipers for cracked or hardened rubber and replace as needed.
While your tires are still "cold" - after it's been parked for several hours - check the tire inflation. Also, look for bubbles, blisters, worn treads, and other weak spots. As heat builds up inside the tires while you drive, those weak spots can lead to a blow-out. They can also lead to slow leaks and frequent flat tires.
Check your coolant and anti-freeze levels. Incorrect levels or mixture levels can cause the engine to overheat. Don't forget to check the fluid level in the radiator.
Other fluids to check are the transmission fluids, brake fluids, power steering fluids, oil, and windshield washer fluids.
Check your air filters - a car straining for air is a car that will overheat.
Have your pressure system checked - this will indicate leaks in the radiator hoses or head gaskets - it's cheaper to replace them than to repair them.
Look for spider webby looking cracks on your engine hoses and belts, and if a belt feels "spongy". They need replacing before the split or break.
Keep a summer emergency kit in your car in case your break down anyway. Bottled water, reflective triangles, flashlight with extra batteries (the nights are hot, too, and sometimes, as an engine cools, it can lead to cracked hoses), a first aid kit, non-perishable snacks, a hat or umbrella, folding fans or battery operated personal fans (the misting fans they sell for sporting events are good), and a cell phone to call for assistance. Don't forget basic car repair items like jacks, jumper cables, work gloves, tow ropes, tie downs, fluorescent or reflective vest, spare tire (that you've kept properly inflated), fire extinguisher, and an assortment of tools.
Keep your tank at least half full.
Spare cash, a phone charger, insurance and registration information, a chainsaw. (around here, I've seen heat stressed trees suddenly drop tree limbs across roads - yo might need to chop one into smaller pieces to move it out of the road so you can drive past.
If you're driving an older car or one of questionable reliability, a AAA membership might be worth it.
If you take a few precautions and keep up the routine maintenance on your car, it can last you a long time and not let you down too often.
EDITED TO ADD: Cyberwizard reminded me about electronics - don't leave laptops, GPS devices, cell phones, kindles, nooks, or other ereaders, blood sugar monitors, digital thermometers, or other electronics in the car - they will melt and become inoperable.
And Richard Cranium recommends duct tape.