For the past several weeks the western portion of the United States is experiencing record heat and dangerously high fire danger. One of the main causes of the heat is the dome of high pressure that is parked over the region. The air sinks under the dome causing the molecules to compress and as they compress they rub together generating friction and therefore heat.
The heat at the surface dries out the landscape so any wildfires that develop will be able to spread quickly. The lack of cloud cover also is a concern as there will be maximum sunlight or solar energy reaching the ground adding to the heat.