It's official. Tuesday's hourly average dewpoint at Tucson International Airport was 57, meaning the monsoon officially started Sunday.

That ties (with two other years) as the seventh earliest monsoon start in records kept by the National Weather Service since 1949.

Weather forecasters will tell you that their job is part art and part science.

The science part — especially when it comes to predicting what will happen more than a couple weeks away — leads them to say things like "There are equal chances that this year's monsoon will be wetter than normal, normal and drier than normal."

That, in fact is what they all said as late as last week.

This week is a different story. We're now hearing about slightly better chances of wetter-than-normal and an early start to the monsoon.

So, if you got the drenching rain at your house today that we got out here at the southside offices of the Arizona Daily Star, you're probably convinced that is true.

There is another official measure of monsoon onset that the National Weather Service abandoned when it began starting the season on June 15 each year. It still keeps the data on its website, however, and it tells us that the monsoon is early.

The Weather Service used to pronounce the monsoon's start when the dewpoint averaged 54 or above for three consecutive days. That happened just barely on Sunday and Monday with readings of 55 and 55. Today the average is again 55 (so far).

That phenomenon usually occurs in the first week of July.

Our weather history also tells us that we may have a wetter than normal monsoon, according to Art Douglass, a monsoon forecaster who compares conditions in the current year with those of the past.

He told UANews: "The bottom line is that when we look at our analog forecast, it is for a wet July, a so-so August and a wet September."

Douglass is currently professor and chair of the department of atmospheric sciences at Creighton University.

He found five summers  — 1984, 1986, 2001, 2006 and 2008 — that look like this one.

"Most of Arizona and New Mexico received more than 110 percent of average during these summers," according to UANews.

To recap: We may have an early monsoon. We can tell because it's raining.