Changing film in rotten conditions works well if you take your coat or long sleeved shirt and pull it over your head and use it as a changing bag to keep the camera out of actively blowing sand or snow. In cold ziplock bags seem to generate more static for me than I am comfortable with. The best protection is to keep the camera buttoned up in poor conditions but it isn't always possible. Don't blow into the camera or you may ice up the film or inside of the camera. Same with the lens, viewfinder and accessories.
Extreme heat is a bear.
Fine dust is more of an enemy than heat. A cooler with padding will help when travelling and a good camera case will help also. That expensive brush you bought works well in these conditions. Not much can be done about it generally, but one solution is to have a spray can of anti static computer spray and gently hose the camera case and around it before you change film. It does work, not perfectly, but well enough to keep extra dust away.