Arizona residents endure a heavy monsoon (summer thunderstorm) season. Arizona experiences more severe storms and rainy weather than other states. When a severe storm spawn a microburst the rainfall levels can be exponential. High winds, dust and severe downpours result in flash flooding that can damage homes and businesses during the monsoon season.

Beginning in 2008, June 15 is established as the first day of monsoon, and September 30 will be the last day – but storms can start sooner and end later. Monsoon safety is a pivotal concern – as temperatures rise and the Gulf fuels the storm clouds, residents in Phoenix and Scottsdale can experience torrential rains and monsoon conditions.

Here are monsoon facts for Arizona. These facts relate to dew point and the meteorological definition of monsoon:

  • The average starting date of the monsoon in Phoenix is July 7.
  • The average ending date of the monsoon is September 13.
  • The earliest start date for the monsoon was June 16, 1925.
  • The latest start date for the monsoon was July 25, 1987.
  • The average date of the first break in the monsoon is August 16.
  • The average total number of monsoon days (where a monsoon day is considered one with an average dew point of 55 degrees or higher) is 56.
  • The greatest number of monsoon days was 99, recorded in 1984.
  • The fewest number of monsoon days was 27, recorded in 1962.
  • The greatest number of consecutive monsoon days was 72, from June 25 through September 4, 1984. This was also the greatest number of consecutive days with dew points of 60 degrees or higher.
  • In Phoenix, normal rainfall during July, August and September is 2.65 inches.
  • The wettest monsoon occurred in 1984 when we had 9.38 inches of rain.
  • The driest monsoon occurred in 1924 with only 0.35 inches.

The facts above were obtained from the National Weather Service, Phoenix Weather Forecast Office.