A monsoonal thunderstorm that hit the Boise area Saturday evening set a rainfall record in drought-parched Southwest Idaho amid dozens of lightning strikes, according to the National Weather Service. And more rain could be on the way Sunday.
The storm rolled into the Treasure Valley late Saturday, bringing a downpour. Jay Breidenbach, a meteorologist with the National Weather Service’s Boise office, said for the entire month of July, the NWS reported .91 inches of rain in Boise, the vast majority of which fell in the first few hours of Saturday’s storm.
By midnight Saturday, the Weather Service recorded .83 inches of rain at its office near the Boise airport — a single-day record for July 31, Breidenbach said.
In a typical July, Boise will see about .21 inches of rain. That means Saturday evening’s storm dumped nearly four times the amount of rain typically seen for the entire month.
“It’s very rare to get any precipitation this time of year,” Breidenbach said. “It’s just dry.”
Closer to Boise’s Foothills, weather station reports showed even heavier rain. Breidenbach said a station on the Crestline Trail, which is part of the Hulls Gulch area, recorded 1.78 inches. Several stations in Southeast Boise, the Boise mountains and one station in Nampa recorded more than an inch, according to precipitation totals from the Weather Service.
“We were cruising in to be well below that normal (July rainfall amount),” Breidenbach added. “It was really an extraordinary rain event — and it’s not over yet.”
The National Weather Service’s flash flood watch remains in effect for the mountain areas surrounding the Treasure Valley until Sunday evening.
The storm also lit up the sky with dozens of cloud-to-ground lightning strikes in Ada County and hundreds more in the surrounding area. Breidenbach said Ada County recorded 113 of the strikes, while Boise County saw 292, Elmore County saw 499 and Owyhee County had 1,117.
Ada County’s total was the fifth-most lightning strikes on record for July.
Despite the intense lightning activity, Breidenbach said few new wildfires were reported. Most of the new blazes were small ignitions reported in the Payette National Forest, which is expected to have more rain Sunday.
“The rain put a big damper on that,” Breidenbach said.
The meteorologist said the storm may have helped push Boise past the worst of summer’s high temperatures. Though the storm system is expected to leave the area by Monday, with higher temperatures quickly returning, the extended forecast shows high temperatures remaining below the triple digits.
“We’re back up into the 90s (on Monday) and that pattern looks like it’s going to continue into the middle of week,” Breidenbach said. “But there’s hope that the heat ebbs by the end of the week and gets below 90. That gets us past the peak of the summer heat.”
According to a tweet from the NWS, July was the hottest on record for Boise by 0.7 degrees. The average temperature for the month was 83.8 degrees, with an average high of 98.6 degrees.
“We’re right past the climatological hottest part of the year,” Breidenbach said. “Hopefully we’ve seen the end of this extreme heat.”