First Freeze of the Season Nears, After a Growing Season Lengthened by Warming

Aug 22, 2017

Overnight low temperatures have dropped down to freezing in some spots around the Interior over the past week, including Denali Park to the south and Eagle to the east. It hasn’t dropped that much yet in the Fairbanks area – but it’s overdue.


National Weather Service climate expert Rick Thoman says depending on where you live in the Fairbanks area, your outdoor garden is living on borrowed time.

Many areas around Fairbanks usually have had their first freeze of the season by now, according to data collected from 2000 to 2016. Goldstream Creek, for example, typically gets its first freeze by Aug. 13 (represented by "a13"). The data suggest the median first-freeze date for the airport is Sept. 15 (or s15).
Credit Rick Thoman/NOAA

Thoman says those areas – “places like the Goldstream Valley bottom, right along the creek; along parts of Piledriver Slough” – are about a week overdue for the first freeze of the season. That’s based on data collected since 2000 through a network of weather stations around Fairbanks. But he says the data suggest higher-elevation areas such as Chena Ridge probably won’t see freezing temperatures for the next week or so.

“As everyone in Fairbanks knows, you just get up (in elevation) a little bit and temperatures during not just in the winter but even overnight lows in the spring and fall can be significantly warmer,” he said. “And that’s what we see in the hills around Fairbanks.”

Coldest Aug. temps:
Goldstream – 36F
Fort Wainwright – 37F
North Pole – 38F
Airport – 45F

Thoman says elevation isn’t the only reason that some areas haven’t gotten their first freeze of the season. Other factors are come into play. He says Gilmore Trail, for example, usually has dropped that low by now, but hasn’t yet. Nor has Fairbanks International Airport, which is located in a relatively low-lying area, but which according to the 16-year dataset is the last place around Fairbanks that drops to 32 degrees Fahrenheit.

“Over the last 17 years, the typical freeze date at the airport has been Sept. 15,” he said. “That’s right in line with what we see in the hills.”

Thoman says data collected from an array of sensors around Fairbanks show a trend toward later first-freeze dates here. He used a different set of data collected since 1977 to show the date of first freeze elsewhere around Alaska.
Credit Rick Thoman/NOAA

Thoman reckons there could be local factors at play around the airport, such as more air movement in that cleared area that elevates the temperature. He says the late median date of first freeze there is reflected in records that date back to 1911, when the University of Alaska Fairbanks' Experiment Farm first began monitoring temperatures around Fairbanks. He says that treasure trove of data shows this area’s growing season is about 10 days longer now than it was a century ago.

“Spring freezes are coming earlier – that is to say, the last freeze is coming earlier – and the first freeze in the fall is coming later as well.”

But Thoman says there’s not enough data to find any evidence of the longer growing-season trend elsewhere around the state.