Colorado’s 2017-2018 water year was warmest ever & second driest
by Allen Best
It was the warmest year in 124 years of records in Colorado and the second driest, too.
A new report from the Colorado Climate Center examined temperature and precipitation records for the 2017-2018 water year, which ended Sept. 30.
“We live in a climate where we’re going to be limited for water. That will happen from time to time. But what set this year apart is the combination of heat and dryness,” says Russ Schumacher, the Colorado state climatologist.
The closest rivals to the heat of the past year were 2002 and a year in the 1930s.
For precipitation, 2002 was actually drier. This past year was bone-dry in the Four Corners area but mostly dry across the state. The notable exception was the state’s northeastern corner, which was somewhat average or above average in precipitation.
But even in the northwestern corner, the Yampa River ran low and the first ever “call” was imposed on water users of the river.
This year’s high temperatures can best be seen as part of trend that began in the 1980s. They also comport with climate change models.
Climate models remain uncertain about precipitation levels, but they do predict greater extremes. This was the third drought winter in 16 years, points out Schumacher, whereas droughts in the 20th century were more widely spaced.
The year’s high was 110 degrees Fahrenheit at Las Animas, along the Arkansas River in southeastern Colorado. The year’s coldest was 29 below zero in late January at Taylor Park, near Crested Butte.
But the individual weather station statistics tell the broader story. Here, in those places with 30 years of data and a few with 124 years, there were more days with record heat than record cold.
“We had several times more warm extremes than cold extremes,” says Schumacher. “That is really the story.”
There were 1,696 case of record high temperatures compared to 560 record low temperatures at the stations.
Even more pronounced were the higher overnight temperatures. There were 2,971 highest minimum temperatures and just 292 lowest minimum temperatures. One night in June, it got down to only 78 degrees F in Grand Junction.
There were also more 90-plus days altogether, including several records. Montrose, located just north of the San Juan Mountains, has an average of 34 of those hot days after 113 years of record-keeping. This year it had 78. Denver had 53 days of 90-plus weather, well shy of the record of 67 set in 2012.
Mountain towns were not immune to heat. Steamboat Springs had 11 days of 90-plus temperatures, above the average of 4 but well short of the record 29 days in 2002.
Dillon, located more than 2,000 feet higher in elevation, kept its record intact. It has yet to hit 90, at least in modern record-keeping. The town was moved to a higher elevation when Dillon Reservoir was built in the late 1950s and early 1960s.