Perhaps a better definition of "Western US" would be in order. June being smoke free is not necessarily so in Colorado. Three of the biggest and most damaging fires in recent history in Colorado were in...June.
The High Park Fire started in early June and was not contained until the end of the month. Burned over 87000 acres, the 2nd largest fire in Colorado history.
The Waldo Canyon fire started in late June and wasn't contained until nearly mid-July. Burned over 18000 acres and forced 32000 people to evacuate their homes. Between those 2 fires, over 600 homes were destroyed.
But perhaps the most destructive was the Black Forest Fire...again in early June. While not the biggest at 14000 acres, this fire alone destroyed over 500 homes.
To say June is smoke free in Colorado would not be accurate every year.
