Monsoon 2021 starts using the dew point rule!
If you lived in the Valley of the Sun before 2008, you likely heard a lot about dew point during the monsoon! The reason for the dew point buzz: the dew point rule! Before 2008, the season was defined to have started after Phoenix had a daily dew point average of 55ºF or higher for three consecutive days. After 2008, fixed start and end dates were determined (June 15th - September 30th).
Even though the dew point rule is not the "official" way to determine the start of the monsoon, it is still fun to track! With that said, Monsoon 2021 started using the "unofficial" dew point rule on June 30th. The daily average dew point was 56º on June 30th, 57º on July 1st, and projected to be in the low 60s on July 2nd! Last year it didn't start until July 22nd.
Using this old dew point system, the average start date for Phoenix was July 7th, but it started as early as June 16th in 1925, and it began as late as July 25th in 1987.
If you lived in the Valley of the Sun before 2008, you likely heard a lot about dew point during the monsoon! The reason for the dew point buzz: the dew point rule! Before 2008, the season was defined to have started after Phoenix had a daily dew point average of 55ºF or higher for three consecutive days. After 2008, fixed start and end dates were determined (June 15th - September 30th).
Even though the dew point rule is not the "official" way to determine the start of the monsoon, it is still fun to track! With that said, Monsoon 2021 started using the "unofficial" dew point rule on June 30th. The daily average dew point was 56º on June 30th, 57º on July 1st, and projected to be in the low 60s on July 2nd! Last year it didn't start until July 22nd.
Using this old dew point system, the average start date for Phoenix was July 7th, but it started as early as June 16th in 1925, and it began as late as July 25th in 1987.