2007 LV’s hottest on record

If you felt like punching one of those "Yeah, but it's a dry heat" people this past summer, the National Weather Service might have an explanation for your irritability.

Last year was the hottest on record for Las Vegas.

By a full degree.

And it appears we'll only get warmer over the next few years.

Monday ended what was a bizarre year for weather in Nevada, with officials recording a final average temperature of 71.1 degrees, shattering the 70.1 degree record set in 2003 and matched in 2005.

The record also came during one of the hottest stretches of years in the city's history.

The average yearly temperature has been hovering well above the Las Vegas average of 68.1 degrees since 1998, the last time the average temperature was below average.

"There's no question this year has been a warm one," said Kelly Redmond, interim director of the Western Regional Climate Center at the Desert Research Institute in Reno.

On top of setting the record for the hottest year, 2007 also saw records set for:

• The hottest average annual low temperature of 60.4 degrees, 4.1 degrees higher than the normal average.

• The hottest July on record, which also turned out to be the hottest month in Las Vegas history.

• The warmest November on record.

And the valley also saw a few highly unusual events. In September, the weather service issued a tornado warning for southwest Clark County, the only such warning in recent memory.

And in mid-March, in what was still the winter season, Las Vegas recorded an official temperature of 90 degrees, a sweltering 21 degrees above average.

The mark also set a record for the earliest 90-degree day of the year.

Nearly every month in 2007 had average temperatures well above average, according to the weather service. Only January and December were cooler than average.

Officials at the weather service attributed the unusually warm weather of the past year to the city's "heat-island" effect, where buildings and streets trap heat during the day and don't cool down at night.

The city's added growth could have been the main factor for the new record, meteorologist Charlie Schlott said.

Official temperatures have been recorded since 1946 at McCarran International Airport, and as the city has built around the airport, temperatures have risen, Redmond said.

But the "heat-island" effect might not be the only thing contributing to the warmer-than-usual temperatures, according to Redmond.

Data from the Western Regional Climate Center, which pools data from more than 100 thermometers statewide, shows that Nevada temperatures, and particularly low temperatures, have been rising at an unprecedented rate over the past 10 years.

"We're seeing this all around the Western states," Redmond said. "They've been warming up for the past 30 years or so."

Even Reno, which is far smaller than Las Vegas, saw an unusually warm year in 2007.

It didn't break its 2003 hottest average temperature record, but Reno weather service meteorologist Alex Hoon said 2007 would place either second or third behind it.

The city did break its record for the warmest August in history, Hoon said.

"It's definitely been a hot, dry year," he said.

Whether it's the "heat-island" effect or global climate change, Nevada nights seem not to be cooling off like they used to.

There was one night in Las Vegas when the temperature didn't get below 90 degrees.

"Ninety-degree minimums (temperatures) are kind of a nice benchmark for what constitutes a really uncomfortable night," Redmond said. "It's so hot that some people have trouble getting to sleep."

And there appears to be no relief in sight, although Schlott said that cyclical weather cycles could unexpectedly bring cooler temperatures in the next decade.

For Redmond, however, the signs point toward more record temperatures.

"If I was a betting person, and you might find some of them in Nevada, it would be toward more warming."

Contact reporter Lawrence Mower at lmower@reviewjournal.com or (702) 383-0440.