A whole new monsoon 'season'

After decades of using dew point readings to mark each year’s monsoon on the calendar, the National Weather Service has changed the rules. Starting this year, the monsoon “season” will begin and end on firm dates, much like hurricane season on the Gulf Coast.

The Weather Service decided that the monsoon “season” will start on June 15th and end on September 30th, regardless of weather conditions. In years past, the first three consecutive days with average dew points of 55 degrees marked the beginning of the monsoon—typically in early July. And the monsoon ended with the last string of three days with such damp dew points--usually in September.

But storms don’t always stay within those boundaries. Last year, a violent monsoon-type storm slammed parts of the East Valley on September 16th, five days after the monsoon officially ended—according to the dew points. The Weather Service says, one of the main reasons for having the season firmly defined on the calendar is to keep the public aware of the monsoon dangers throughout the time period when summer storms can happen.

Sarah Walters explains new season