Frost history / Copco #1 Dam, CA
Copco #1 Dam, CA: frost dates by year
Last spring and first fall frost at NOAA station USC00041990, 2011 to 2021, measured from daily minimum temperatures.
Elevation 2,703 ft, 41.980, -122.338. Download the data (JSON), NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | May 1 | Oct 12 |
| Earliest | Apr 19 (2018) | Oct 1 (2017) |
| Latest | Jun 11 (2017) | Nov 16 (2014) |
| Trend | 22.0 days earlier per decade | 2.8 days earlier per decade |
| Years with data | 11 | 11 |
At 28°F (hard freeze) the median last spring date is Apr 12 and the median first fall date is Oct 27.
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 |
|---|---|---|---|---|
| 2021 | Apr 27 | Oct 12 | Mar 30 | Oct 12 |
| 2020 | May 4 | Oct 22 | Apr 2 | Oct 27 |
| 2019 | May 1 | Oct 3 | Mar 31 | Oct 28 |
| 2018 | Apr 19 | Oct 30 | Apr 4 | Oct 30 |
| 2017 | Jun 11 | Oct 1 | Jun 10 | Oct 12 |
| 2016 | Apr 26 | Oct 2 | Apr 26 | Oct 2 |
| 2015 | Apr 24 | Nov 4 | Apr 12 | Nov 6 |
| 2014 | Apr 28 | Nov 16 | Apr 1 | Nov 17 |
| 2013 | May 22 | Oct 2 | Apr 16 | Nov 4 |
| 2012 | May 5 | Oct 21 | Apr 27 | Oct 21 |
| 2011 | Jun 7 | Oct 6 | Jun 3 | Oct 27 |
"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.