LAS VEGAS (KTNV) — It won't be long before the North American monsoon season arrives in the Southwest, bringing both potential flooding risks and water conservation opportunities to Las Vegas.
Starting in mid-June and lasting until September, the monsoon season begins as the land warms up and winds shift to bring moisture from the ocean.
But what makes a monsoon different than any other type of rain?
"That moisture is the fuel for the thunderstorms," a meteorologist explained.
"The high pressure gets kind of centered over the Four Corners. The flow around it is clockwise, and so that allows moisture to be drawn over across from the Gulf and up north into our areas."
That's called onshore flow, which brings moisture into Las Vegas from the Gulf of Mexico, Gulf of California, and the eastern Pacific. Combined with hot temperatures and mountain terrain, it creates the perfect conditions for potent thunderstorms.
Just two years ago, 2023 was one of the wettest years on record for Las Vegas with 2.88 inches of rain.
However, thunderstorms don't always deliver significant moisture. Many locals remember the "nonsoon" of last year when the area received only 0.8 inches of rain.
What varies from year to year is the location of high pressure and how monsoonal moisture moves around it.
"If it's more overhead, that's usually an indicator that it's going to be hot, but if it's closer to that Four Corners area, that's when we'll be looking for monsoon storms," the meteorologist said.
In the Las Vegas Valley, flooding can occur quickly. The soil is hard, dry, and compacted, so when heavy rain arrives, it's like water poured on concrete.
"You can get flash flooding in an hour. There's been events that we've had in Las Vegas Valley where we've gotten an inch of rain in like almost 15 minutes," the meteorologist said.
To manage these flood risks, I met with Regional Flood Control District's chief engineer Andrew Trelease at the massive Silverado Ranch Detention Basin in the Southwest Valley. This $23 million project was completed in 2023.
"This detention basin fills up with water like a bathtub and then drains it very slowly downstream, so all the raging, violent water from upstream in those concrete channels comes in here," Trelease said.
The basin can hold 294 acre-feet of water, equivalent to about 300 football fields 30 stories high. The system doesn't require pumps or personnel to manage it; it's entirely powered by gravity.
"We've completed 713 miles of channels and storm drains in Clark County and 111 detention basins just like this one. We still have another 226 miles of channels and storm drain to complete," Trelease said.
Trelease told me 39 more detention basins are planned as part of an infrastructure project that will take about 30 years to finish.
The flood control infrastructure represents significant progress from earlier decades.
"If the Las Vegas valley didn't have any flood control infrastructure," Trelease said," We had that before in the '80s and '90s or really in the '70s also, as we were developing. And the washes would just fill up with water, rage downstream, cars got swept off the road, buildings could fall into the wash. People were killed," Trelease said.
Beyond flood control, the monsoon season also presents water conservation opportunities. Bronson Mack from the Southern Nevada Water Authority emphasized the importance of utilizing rainfall.
"It's the water that we use outdoors that we only get to use one time in a place like Las Vegas," he said.
"Our indoor water use is a perpetual loop," Mack added. "This is why it is so important that when it rains, turning off that irrigation system and getting some real water savings, not just for your water bill, but also for the community as a whole."
When major storms move through the area, the water authority will remind residents to turn off their sprinklers and conserve water.
This story was reported on-air by a journalist and has been converted to this platform with the assistance of AI. Our editorial team verifies all reporting on all platforms for fairness and accuracy.
