Delavan Wwtp, WI: frost dates by year

Last spring and first fall frost at NOAA station USC00472051, 2011 to 2025, measured from daily minimum temperatures.

Elevation 882 ft, 42.636, -88.661. Download the data (JSON), NOAA daily records

Summary at 32°F

	Last spring frost	First fall frost
Median	Apr 30	Oct 19
Earliest	Apr 16 (2025)	Oct 2 (2011)
Latest	May 15 (2016)	Oct 30 (2023)
Trend	8.0 days earlier per decade	8.9 days later per decade
Years with data	13	14

At 28°F (hard freeze) the median last spring date is Apr 18 and the median first fall date is Oct 31.

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	Apr 16	Oct 23	Apr 16	Oct 24
2024	Apr 25	Oct 16	Mar 29	Nov 26
2023	Apr 26	Oct 30	Apr 26	Oct 30
2022	Apr 27	Oct 8	Apr 17	Oct 19
2021	May 11	Oct 22	Apr 22	Nov 3
2020	May 12	Oct 20	Apr 18	Oct 30
2019	no data	Oct 25	no data	Nov 1
2018	Apr 30	no data	Apr 29	no data
2017	May 7	Oct 29	Apr 1	Nov 6
2016	May 15	Oct 14	Apr 12	Nov 12
2015	May 2	Oct 17	Apr 24	Oct 17
2014	Apr 23	Oct 10	Apr 23	Nov 2
2013	May 14	Oct 22	Apr 20	Oct 22
2012	Apr 27	Oct 8	Apr 13	Oct 27
2011	no data	Oct 2	no data	Nov 4

"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.