Fire season peaks out in the southwest part of the United States in the month of June, but many years fire season can last well into July or even August. The combination of hot weather, and very dry conditions, combined with late spring winds makes the month of June the peak month of the year.
Monsoon season on average starts July 12, but this year it appears to have started at least a week early. The definition of a monsoon is a seasonal wind shift. It is this wind shift that is responsible for bringing in moisture latent air. This air then runs into hot desert air, and boom, a thunderstorm is born.
This seasonal wind shift originates from an area of high pressure that sets up across the southwestern U.S. The clockwise flow of air around the high taps into moist air to the south and, draws it north and then east.
It is not only the rain that helps out with suppressing western wildfires, but the higher levels of humidity in the air that the monsoon brings. Fires not only love dry vegetation, but also thrive off dry air.
The beginning of monsoon season is not always obvious, but one definition is when the city of Phoenix records a dewpoint of a least 50 degrees three days in a row.
While the area of high pressure is generally parked across the southwest, it is still prone to wobble. This wobble will bring breaks, and bursts of rainfall to the region through at least September, or until the first strong cold front of the season cuts of the moisture.