We don't often see a monsoon storm like the whopper that hit Tempe Thursday.

In fact, Thursday night's rainfall was so rare and so extreme, it even gets a title: A "1,000-year rainfall event!"

[RELATED: Overnight monsoon storm causes heavy flooding, road closures in Phoenix area]

State climatologist Nancy Selover explains that that means that amount of rain falling in one hour at that location has a one in 1000 chance of occurring any given year.

It’s a probability. So it’s also referred to as a 1,000-year event.

It doesn’t mean it can only happen once in 1,000 years, but it’s got a very low probability of happening any year.

Another way to think about it is that 99.9 percent of the time, an event like this won't ever happen, meteorological researcher Shane Hubbard has explained.

[SPECIAL SECTION: Arizona Monsoon 2018]

The data was based on the gauge in Tempe near Rural and the 60 that reported 3.63” in an hour.

Several roads were flooded around the Tempe area, including the U.S. 60 in Tempe, causing road closures to be put in place.

[SPECIAL SECTION: Outage maps]

According to the Arizona Department of Transportation, the U.S. 60 was closed in both directions around 1:30 a.m. after flooding had forced a closure on both directions of the highway. The freeway was reopened at 4:30 a.m.

The monsoon storm also caused massive outages in the east Valley. According to the Arizona Public Service, over 700 customers were without power at the height of the storm.

The storm also wreaked havoc at Lake Pleasant, where more than a dozen boats were damaged.

[RELATED: Monsoon hits Lake Pleasant, damages more than a dozen boats]

In summary, it was a pretty rare storm. And it was a pretty significant one.

Weather spotters around the Valley were on high alert, with reports of: tree limbs of 6-8 inches in diameter snapped reports of zero visibility in some areas heavy street flooding with water backing up into people's yards street flooding with water exceeding curbs dense blowing dust[SPECIAL SECTION: AZ Family Weather]

We’re still getting remnants of what is now Tropical Storm John, so any storms that develop have the potential to produce more flooding, along with strong to severe wind gusts and frequent lightning.

Two sunk and and about 15 other boats were damaged at Lake Pleasant during Thursday night storm. Picture from Sue Barsell. https://t.co/IRo2TBsnQa #azwx pic.twitter.com/OYkk2A6ISa— Ian Schwartz (@SchwartzTV) August 10, 2018
#Update Good News... US 60 EB ramp to Loop 101 NB reopened. It was shut down overnight b/c mud covered the road. #eastvalley #azfamily pic.twitter.com/usrVJ8WnPt— Gina Maravilla (@GinaMaravillaTV) August 10, 2018
* STORM NEWS * This is what the US 60 looks like at US 60 westbound and Rural. #phxtraffic pic.twitter.com/xS4GuyTyql— Arizona DOT (@ArizonaDOT) August 10, 2018
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