Your vaporizer and its batteries hold a large amount of energy in a compact, small space. So, just as you would do with other devices powered by lithium-based batteries, never leave your vaporizer in your hot car or exposed to the sun’s heat.
You should also avoid charging your batteries in a hot car with the cigarette lighter adapter or USB socket. When charging your batteries during the summer, monitor them with extra-close attention.
I've found I can still charge and vape in the car at the same time if I hold my device by the AC every now and then. Some devices, like the Wismec Presa, tell you the temperature of the circuit board. This helps a lot, but your hand will tell you if your device is too hot as well.
Keep your e-liquid out of direct sunlight. Sunlight can damage your e-liquid and cause it to darken, the ingredients to separate, weaken the nicotine and make it taste bad.
E-liquids thin slightly in warmer environments. If your device has a variable voltage, it might help to drop the voltage down a bit. You should also make sure that the threaded parts of your tanks or clearomizers are connected and tightened properly; when e-liquids thin, their delivery systems have an increased likelihood of leaking.
Not only do e-liquids thin when heated, they also expand in cooler environments. So, if you’re filling your tanks or clearomizers when the temperatures are a little lower, like at night or in the morning, use a smaller amount than you normally would to allow for expansion—especially if you won’t be vaping for a while.
It’s generally a good idea, no matter the season, to store your spare batteries and bulk e-liquids in a dark, cool location. Keeping them cool and out of direct sunlight means your juice stays just as yummy and fresh as the day you brought them home.
Vaping tends to dehydrate you. In the summer when you're out playing in the sun, be sure to have extra liquids to rehydrate yourself as sweating and vaping will gang up on you.