Gas canisters are designed to easily withstand all temperatures naturally occurring in our latitudes. Gas canisters may perfectly safely be left outside in the hottest summer sun and in the harshest winter frost. Even if left in a hothouse, the gas inside would never become dangerously hot.
But beware! The blue camping gas canisters are made of much thinner metal than propane gas canisters. Camping gas canisters must never be left exposed to the sun inside your car!