Question of the Day - 02 October 2017

With all the devastating weather events lately, what's the worst that has and could happen in Vegas? 

In a nutshell, the worst common weather event is flash floods. Even though the average rainfall in Las Vegas is 4.5 inches, the summer monsoon season can often account for a quarter of that in a single storm. Vegas is at the tail end of weather systems that blow in from the south and the Gulf of California and the southeast and the Gulf of Mexico. And because of the hard-packed desert soil, plus all the pavement in the city, that ground can’t absorb anywhere near that much heavy rainfall, so streets can get flooded very quickly.

It’s not like the flooding you see in towns and cities where rivers overflow and inundate the whole place, but streets with depressions or troughs can entertain three feet of runoff in places. The flood-control system throughout the valley has come a long way in the past 20 years, but flash floods can still be very dangerous when they hit.  

Winds can also get fairly extreme in southern Nevada. The last couple days of March 2017 saw ferocious winds of up to 84 miles per hour (hurricane-force winds start at 74 mph)—delaying flights in and out, blowing over tractor-trailers, uprooting trees that blocked streets, reducing visibility to nearly zero, causing widespread power outages, and destroying the Main Street Station marquee.

But unlike Phoenix, where intense dust storms, known as “haboobs,” blanket the city, can be 6,000 feet high and 100 miles long, and blot out the sun, Las Vegas is protected by the surrounding mountains. 

Las Vegas also sits atop a number fault lines, which we’ve covered in several previous QoDs. Earthquakes can and do happen, but they’re mild and infrequent.

It snows in the valley on occasion; when it does, driving is treacherous. But the snow doesn’t remain on the ground for long.

Tornadoes are rare, but do occur. The last one was on August 6, 2014; the one before that was on April 21, 2001. But they’re short-lived and register the lowest rating on the Enhanced Fujita scale.

Otherwise, temperatures can be extreme. The record high temperature of 117 degrees has been achieved four times: July 24, 1942, July 19, 2005, June 30, 2013, and June 20 of this year. It’s hit 116 on 17 different days and 115 degrees 36 times.

The record coldest temperature is 8 degrees, on January 13, 1963. That’s a record temperature swing of 109 degrees.