DENVER — Wednesday was Denver's fourth consecutive 60-degree January day. Though this weather pattern may seem strange, it's not very unusual for temperatures to reach 60 degrees in Denver during the first month of the year — but it would be atypical if this warm streak continues into Thursday.
There has been at least one 60-degree day in January for 21 of the last 24 years. However, last year was one of the three in which no January day reached 60 degrees. The temperatures during this warm week are not extreme either. They had to get into the 70s to break records on Monday and Tuesday, and the record for Thursday is 73 degrees.
So, no obvious climate signal there.
But if the high temperature reaches 60 degrees again on Thursday, we will get into some extremely unusual territory because that would make five consecutive 60-degree days. That’s something that has only happened in Denver between Jan. 1 and Feb. 2 in three other years since 1900. It happened twice in 1935.
The forecast for Thursday is 62 degrees.
Usually, at least one weak cold front moves through during this very active part of the winter to break up a 60-degree streak like this one. While it's very unusual that there was no front this time around, there's still nothing in the data that would suggest that climate change is responsible for that — it just means this is an unusual weather pattern that only comes around about once every 31 years (four times since 1900 counting this year).
You have to look beyond the weather to see the impacts of climate change.
An analysis by the Colorado Climate Center shows that the average January temperature in Colorado has warmed by 3.8 degrees since 1895, and it’s 3.9 degrees warmer on the northern Front Range.
So, the answer is no, climate change did not cause this unusually warm streak in winter weather — but the research shows it does increase the odds that it will happen. This could be the beginning of a climate trend, but we'll have to wait to see if these 60-degree winter streaks get more frequent in the years to come.
And, keep in mind: climate change does not decrease the odds of an extreme cold weather event either. Because of the polar vortex a couple of weeks ago, this January will still end much colder than average in Denver despite finishing on such an unusually warm streak.
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