Recordsetting heat to move out

Sweater-weather next up for county

The Front Range simmered through another day of record breaking heat as Boulder held on to the double digits with a whiteknuckle grip and a mid-afternoon high of 97 degrees Thursday, while the Vance Brand Municipal Airport in Longmont logged a record high of 101.

Thursday’s high temperatures replaced the previous records set for the same day in September of 93 degrees in Boulder in 1959, and 96 degrees in Longmont in 1988.

A cold front blowing in late Thursday evening was expected to usher out the unprecedented September heat wave, and the cooler temperatures in its wake may justify that pumpkin spice latte, or at least a sweater, by Saturday.

According to Boulder meteorologist Matt Kelsch, the Boulder area was to experience a late afternoon downslope on Thursday of warm wind from the west, preceding the cold front from the north that was forecast to arrive later in the evening, reminiscent of the late December weather pattern that produced the Marshall Fire.

While not every day this month has broken a high temperature record, the National Weather Service has recorded temperatures in Boulder over 90 degrees every day this month through Thursday, and that is a first. The normal average daily temperature for the first week of September ranges from the upper 70s to mid-80s.

Bob Hansen, a Boulder-based meteorologist and journalist for Yale Climate Connections, attributed the lingering heat wave to a jet stream that’s been “shunted to the north,” but cumulatively, this week’s weather is a hallmark of a warming climate.

“Now we’re seeing the hot seasons spread out as we experience this warming climate. It’s not just intense heat in July, but the shoulder seasons of the late

summer and early fall are getting more intense,” Hansen said.

This recent weather is attributed to a La Nina weather pattern that’s in its third year, which Hansen said only occurs every 25-30 years. Whereas El Nino patterns trend toward wetter weather, La Nina characteristically means drier and warmer autumn weather in the southwest.

“Last year was the epitome of that,” Hansen said. “We can’t say for certain how long it will persist, but it raises the likelihood of a dry autumn, and the odds of an October dump of wet weather are highly unlikely.”

But as the tired saying goes, wait a minute and the weather will change. After the cold front moves out Sunday, temperatures were forecast to climb back up into the upper 80s next week.

Hansen said there’s still the potential for another few days over 90.

“I wouldn’t rule out another 90 degree day or two, but this is about as late as we ever get in the upper 90s,” he said.

“I seriously doubt we’ll get another solid week of this heat. I think we’re over the hump.”