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Will it freeze in Clear Lake in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Tonight: 31°F (Thu, Nov 5, 6:00 PM CST to Fri, Nov 6, 6:00 AM CST).
Tonight: forecast low 31°F. Freeze.
NWS forecast period: Thu, Nov 5, 6:00 PM CST to Fri, Nov 6, 6:00 AM CST.
6 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 31°F Freeze · Mostly Cloudy
- Fri, Nov 6 25°F Hard freeze · Partly Cloudy
- Sat, Nov 7 32°F Freeze · Partly Cloudy
- Sun, Nov 8 35°F Frost possible · Mostly Clear
- Mon, Nov 9 36°F Frost possible · Mostly Clear
- Tue, Nov 10 35°F Frost possible · Mostly Cloudy
- Wed, Nov 11 37°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 Clear Lake
The median first fall hard-freeze date (28°F) is October 11, from NOAA’s 1991–2020 Climate Normals at Mason City Municipal Airport. 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 30 · May 11 · May 25 | Sep 10 · Sep 24 · Oct 5 | 134 days |
| 32°F freeze | Apr 19 · May 3 · May 15 | Sep 18 · Oct 1 · Oct 15 | 150 days |
| 28°F hard freeze | Apr 9 · Apr 24 · May 7 | Sep 27 · Oct 11 · Oct 23 | 169 days |
Average high temperature by month
1991–2020 normals at Mason City Municipal Airport
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 Clear Lake, IA come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Mason City Municipal Airport (station USW00014940, elevation 1,225 ft), 2.7 mi from Clear Lake. 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 Clear Lake
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Mason City, IA | 8.7 mi | Apr 29 | Oct 7 |
| Charles City, IA | 35 mi | Apr 30 | Oct 6 |
| Albert Lea, MN | 36 mi | Apr 27 | Oct 9 |
| Austin, MN | 42 mi | Apr 30 | Oct 5 |
| Iowa Falls, IA | 43 mi | Apr 28 | Oct 10 |
| Algona, IA | 43 mi | Apr 30 | Oct 6 |
| Webster City, IA | 52 mi | May 3 | Oct 2 |
| Waverly, IA | 54 mi | Apr 27 | Oct 10 |
| Fort Dodge, IA | 59 mi | Apr 28 | Oct 8 |
| Cedar Falls, IA | 63 mi | Apr 27 | Oct 10 |
Frequently asked questions
When is the last frost in Clear Lake?
On average, the last spring frost (32°F) in Clear Lake is around May 3. In about 1 year in 10 it comes after May 15, and in 9 years in 10 it comes after April 19.
When is the first frost in Clear Lake?
The first fall frost (32°F) usually arrives around October 1. There’s a 10% chance of a freeze by September 18 and a 90% chance by October 15.
Can it frost in Clear Lake 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 11.
What growing zone is Clear Lake?
Clear Lake 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 50428. See growing zones in Iowa.
More: all Iowa frost dates · Iowa growing zones · frost vs. freeze