Defining monsoon using the old method

Posted on Jul-10-2017 at 18:48:00

For those of you that lived in Phoenix before 2008, you likely remember all the buzz about the dew point and the start of monsoon. That is because the monsoon used to officially start in Phoenix when the daily average dew point reached 55 degrees or higher for three consecutive days.

Starting in 2008, the Arizona Monsoon became defined by finite start and end dates. Under this new “system” the start date of the Monsoon is June 15th, and it ends on September 30th.

[Read more: What is the monsoon?]

But it is still fun to track the daily average dew point, so here we go! Using the old dew point rule, on average, the monsoon in Phoenix starts on July 7th. The earliest ever start to monsoon was June 16th back in 1925, and the latest recorded start occurred on July 25, 1987.

So what about this year? Well… the past two days in Phoenix have had a daily average dew point of 55 degrees or greater. As a result, if Phoenix can have another average at/above 55 degrees tomorrow (Tuesday), Monsoon 2017 would have started on July 9th using the old rules. That is just two days past the average.

[Read more: What is dew point?]

If you have any weather questions, be sure to send them my way via e-mail or tweet me @mattpaceweather