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Will it freeze in Decorah in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Fri, Nov 6: 26°F (Fri, Nov 6, 6:00 PM CST to Sat, Nov 7, 6:00 AM CST).
Tonight: forecast low 33°F. Frost possible.
NWS forecast period: Thu, Nov 5, 6:00 PM CST to Fri, Nov 6, 6:00 AM CST.
4 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 33°F Frost possible · Mostly Cloudy
- Fri, Nov 6 26°F Hard freeze · Partly Cloudy
- Sat, Nov 7 34°F Frost possible · Partly Cloudy
- Sun, Nov 8 36°F Frost possible · Clear
- Mon, Nov 9 40°F Above 36°F · Mostly Clear
- Tue, Nov 10 37°F Above 36°F · Partly Cloudy
- Wed, Nov 11 38°F Above 36°F · Partly Cloudy
Overnight lows from the National Weather Service forecast for this location. This covers the available forecast window, not the first freeze of the whole season. Frost can form above 32°F on clear, calm nights.
Frost and freeze probabilities
Freeze dates shift from year to year. Spring percentages describe the chance of a freeze after the stated date; fall percentages describe the chance of a freeze by that date. The 10% spring date is the cautious one: a later freeze happens about 1 year in 10.
These dates describe historical probabilities, not this year’s forecast or the earliest and latest possible freezes. Different weather stations or probability thresholds can produce different published dates for the same city.
Average first hard freeze in Decorah
The median first fall hard-freeze date (28°F) is October 17, from NOAA’s 1991–2020 Climate Normals at Decorah. This is the 50% probability date, not a forecast for this year.
| Temperature | Last spring date 90% · 50% · 10% chance of a later freeze | First fall date 10% · 50% · 90% chance of an earlier freeze | Season |
|---|---|---|---|
| 36°F frost possible | Apr 29 · May 13 · May 26 | Sep 15 · Sep 28 · Oct 10 | 138 days |
| 32°F freeze | Apr 19 · May 3 · May 16 | Sep 25 · Oct 7 · Oct 21 | 157 days |
| 28°F hard freeze | Apr 7 · Apr 22 · May 8 | Oct 3 · Oct 17 · Oct 31 | 178 days |
Average high temperature by month
1991–2020 normals at Decorah
Average low temperature by month
Months with lows near or below freezing carry frost risk
Where these frost dates come from
The frost dates for Decorah, IA come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Decorah (station USC00132110, elevation 860 ft), 0.6 mi from Decorah. Local conditions (valleys, hilltops, distance to water, city heat) can shift frost dates by days or weeks. The hardiness zone is from the 2023 USDA Plant Hardiness Zone Map (USDA ARS and Oregon State University PRISM). See our methodology.
Frost dates near Decorah
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Prairie du Chien, WI | 37 mi | Apr 28 | Oct 12 |
| La Crescent, MN | 43 mi | Apr 15 | Oct 28 |
| Oelwein, IA | 44 mi | Apr 30 | Oct 9 |
| La Crosse, WI | 46 mi | Apr 27 | Oct 13 |
| Charles City, IA | 48 mi | Apr 30 | Oct 6 |
| Onalaska, WI | 50 mi | Apr 23 | Oct 17 |
| Winona, MN | 52 mi | Apr 21 | Oct 19 |
| Stewartville, MN | 52 mi | Apr 30 | Oct 6 |
| Waverly, IA | 53 mi | Apr 27 | Oct 10 |
| Holmen, WI | 53 mi | Apr 23 | Oct 17 |
Frequently asked questions
When is the last frost in Decorah?
On average, the last spring frost (32°F) in Decorah is around May 3. In about 1 year in 10 it comes after May 16, and in 9 years in 10 it comes after April 19.
When is the first frost in Decorah?
The first fall frost (32°F) usually arrives around October 7. There’s a 10% chance of a freeze by September 25 and a 90% chance by October 21.
Can it frost in Decorah after the last frost date?
Yes. Frost can form on clear, calm nights even when the air stays above 32°F. Temperatures of 36°F or lower, cold enough for frost on exposed plants, have a 50% chance of occurring after May 13.
What growing zone is Decorah?
Decorah is in USDA Plant Hardiness Zone 5a (average annual extreme minimum temperature −20 to −15°F), based on the 2023 USDA map for ZIP code 52101. See growing zones in Iowa.
More: all Iowa frost dates · Iowa growing zones · frost vs. freeze