In addition to safety reasons, for LP (propane) grills, leaving the tank valve on can easily lead to a grill going into reduced gas flow state known as bypass. When in bypass, the grill wont reach its proper cooking temperature range, often getting no hotter than 250 to 300F. Click here for info on bypass.

Can you remove small propane tanks?

Yes, generally the small propane canisters will last several uses depending on the duration of cooking time used on the stove. Yes, remove the canister during transport and storage.

Can gas grill stay outside all winter?

It is absolutely 100% okay to leave a gas grill outside in winter, under one condition: The temperature cant be lower than -44 degrees F. Anything less is too cold for a propane grill to produce the vapor needed.