Frost history / Keystone Ridge, AK
Keystone Ridge, AK: frost dates by year
Last spring and first fall frost at NOAA station USC00504621, 1996 to 2025, measured from daily minimum temperatures.
Elevation 1,600 ft, 64.916, -148.271. Download the data (JSON), NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | May 16 | Sep 21 |
| Earliest | Apr 24 (2005) | Aug 15 (2000) |
| Latest | Jun 22 (2002) | Sep 30 (2001) |
| Trend | 2.3 days earlier per decade | 5.6 days later per decade |
| Years with data | 29 | 28 |
At 28°F (hard freeze) the median last spring date is May 7 and the median first fall date is Sep 28.
The trend is a straight-line fit through the years with a freeze. A positive spring trend means the last frost now comes later. Short or patchy records give noisy trends.
Chart
Last spring frost (32°F)
First fall frost (32°F)
Dots are single years. The gray line is the median, the green line the fitted trend.
Year by year
| Year | Last spring 32°F | First fall 32°F | Last spring 28°F | First fall 28°F |
|---|---|---|---|---|
| 2025 | May 15 | Sep 22 | Apr 29 | Sep 28 |
| 2024 | May 10 | Sep 27 | May 7 | Oct 2 |
| 2023 | Jun 2 | Sep 18 | Apr 27 | Sep 28 |
| 2022 | May 16 | Sep 27 | May 11 | Oct 9 |
| 2021 | May 29 | Aug 28 | May 1 | Sep 20 |
| 2020 | May 18 | Sep 25 | May 17 | Oct 11 |
| 2019 | May 7 | Sep 22 | May 5 | Sep 22 |
| 2018 | May 7 | Sep 28 | May 7 | Oct 7 |
| 2017 | May 26 | Sep 29 | Apr 27 | Sep 30 |
| 2016 | May 17 | Sep 26 | Apr 16 | Oct 3 |
| 2015 | May 2 | no data | Apr 23 | no data |
| 2014 | May 20 | Aug 29 | Apr 12 | Aug 31 |
| 2013 | May 20 | no data | May 20 | no data |
| 2012 | May 15 | Sep 11 | May 3 | Sep 29 |
| 2011 | May 13 | Sep 26 | May 11 | Sep 30 |
| 2010 | May 6 | Sep 22 | May 5 | Sep 23 |
| 2009 | May 16 | Sep 20 | Apr 25 | Sep 22 |
| 2008 | May 1 | Sep 21 | May 1 | Sep 26 |
| 2007 | May 13 | Sep 21 | May 13 | Sep 22 |
| 2006 | Jun 5 | Sep 29 | Jun 4 | Sep 30 |
| 2005 | Apr 24 | Aug 31 | Apr 21 | Sep 28 |
| 2004 | May 9 | Sep 4 | May 8 | Sep 15 |
| 2003 | May 23 | Sep 12 | May 17 | Sep 13 |
| 2002 | Jun 22 | Sep 9 | May 10 | Sep 10 |
| 2001 | May 24 | Sep 30 | May 12 | Sep 30 |
| 2000 | May 27 | Aug 15 | May 15 | Sep 17 |
| 1999 | May 18 | Sep 23 | May 5 | Sep 25 |
| 1998 | May 12 | Aug 19 | May 12 | Sep 29 |
| 1997 | May 31 | Sep 28 | May 7 | Oct 2 |
| 1996 | no data | Aug 27 | no data | Sep 21 |
"none" means the station recorded no freeze at that threshold in that half of the year. "no data" means more than 10% of the season's daily readings were missing. Years with no usable data are left out. See the methodology for the rules, and the ZIP lookup for 1991 to 2020 frost probabilities.