After dry monsoon season, hurricane set to bring Southern Nevada heavy rain

Las Vegas is in the path of a rapidly intensifying tropical storm that is expected to cause temperatures in Las Vegas to tumble and bring flooding in the coming days.

A tropical storm along the west coast that developed into Hurricane Hilary Thursday is expected to bring periodic rainfall to Southern Nevada, some of which may be heavy with lightning strikes, according to the National Weather Service.

The significant shift in weather is unusual for August in the southwest, say meteorologists.

“Tropical weather systems do occasionally affect our area during August and September, but it isn’t common,” said Daniel Berc, a meteorologist for the National Weather Service’s Las Vegas Office.

Nevada’s monsoon season typically lasts from June to mid-September, but this summer has proved to be pretty sleepy, say meteorologists. A large contrast to 2022, which had the most active monsoon season on record in the Vegas valley, dating back to 1937. One powerful thunderstorm even washed out roads and stranded more than 1,000 visitors in Death Valley National Park last year.

Heavy August rains after a dry monsoon follow a trend of whiplash weather in Southern Nevada this year. 

June this year proved to be one of the coldest on record with only one day of triple-digit temperatures in contrast to the typical 16 days of triple-digit temperatures, making it unusually cool, said Nevada state climatologist Stephanie McAfee. What followed the next month was the hottest July ever recorded in Las Vegas. 

While it’s impossible to trace any particular weather event to human-caused climate change, the trend is undeniably linked, say climate scientists.

“We can’t really attribute a single weather event to climate change. However, with climate change, we can expect more frequent storms at greater intensity,” Berc said.

Hilary will likely stay close enough to land to cause flash flooding and washouts in Southern Nevada, as normally dry stream beds fill with rushing water. 

A stream of moisture from the storm is forecasted to continue northward through the Great Basin as a post-tropical depression, bringing rain to parts of western Nevada as well. Several rural towns in the Southern Nevada area are under a flood watch warning, including Tonopah and Beatty.

In the Las Vegas metro area, flooding from heavy rain is expected to affect roads and air traffic over the weekend and into early next week. 

Las Vegas typically receives 0.32 of an inch of rain during the entire month of August, but moisture from the incoming storm system may bring “an inch or more of rain with the possibility of much more,” said Berc. 

The abundant atmospheric moisture will also cause cooler temperatures than typical. Following a high-temperature of 107 degrees in early August, temperatures in Las Vegas are expected to settle into the low-to-mid 80s over the weekend and Monday. The reprieve from triple-digit weather, however, will be short-lived.

“I would expect that once the effects of the tropical influence fade next week, we will warm back up to typical summer temperatures,” Berc said.

As of Thursday, Hurricane Hilary in the Eastern Pacific Ocean strengthened to a Category 4 hurricane and was less than 600 miles from the southern tip of Mexico’s Baja peninsula, according to the National Weather Service.

Hurricane Hilary is not expected to be a hurricane once it makes landfall, say forecasters, as most tropical systems tend to quickly lose wind intensity after making landfall on the west coast due to mountainous terrain. However, heavy rain can persist for hundreds of miles.

“The moisture will cover a large area, and all of Nevada will have enhanced moisture, although the greater concern will be in southern Nevada and California,” Berc said.