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Will it freeze in Decatur in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Fri, Nov 6: 30°F (Fri, Nov 6, 6:00 PM CST to Sat, Nov 7, 6:00 AM CST).
Tonight: forecast low 40°F. Above 36°F.
NWS forecast period: Thu, Nov 5, 6:00 PM CST to Fri, Nov 6, 6:00 AM CST.
3 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 40°F Above 36°F · Chance Drizzle
- Fri, Nov 6 30°F Freeze · Mostly Clear
- Sat, Nov 7 31°F Freeze · Mostly Clear
- Sun, Nov 8 34°F Frost possible · Clear
- Mon, Nov 9 39°F Above 36°F · Mostly Clear
- Tue, Nov 10 38°F Above 36°F · Mostly Clear
- Wed, Nov 11 39°F Above 36°F · Mostly Clear
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 Decatur
The median first fall hard-freeze date (28°F) is November 3, from NOAA’s 1991–2020 Climate Normals at Decatur Water Treatment Plant. 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 12 · Apr 26 · May 13 | Sep 30 · Oct 14 · Oct 27 | 170 days |
| 32°F freeze | Apr 1 · Apr 14 · May 1 | Oct 11 · Oct 24 · Nov 5 | 192 days |
| 28°F hard freeze | Mar 18 · Apr 3 · Apr 17 | Oct 20 · Nov 3 · Nov 19 | 214 days |
Average high temperature by month
1991–2020 normals at Decatur Water Treatment Plant
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 Decatur, IL come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Decatur Water Treatment Plant (station USC00112193, elevation 639 ft), 2.1 mi from Decatur. 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 Decatur
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Mount Zion, IL | 5.6 mi | Apr 16 | Oct 22 |
| Clinton, IL | 20 mi | Apr 20 | Oct 16 |
| Monticello, IL | 22 mi | Apr 23 | Oct 13 |
| Taylorville, IL | 29 mi | Apr 12 | Oct 20 |
| Lincoln, IL | 31 mi | Apr 20 | Oct 16 |
| Pana, IL | 33 mi | Apr 17 | Oct 23 |
| Mahomet, IL | 37 mi | Apr 23 | Oct 13 |
| Springfield, IL | 38 mi | Apr 15 | Oct 22 |
| Savoy, IL | 39 mi | Apr 19 | Oct 17 |
| Champaign, IL | 39 mi | Apr 15 | Oct 24 |
Frequently asked questions
When is the last frost in Decatur?
On average, the last spring frost (32°F) in Decatur is around April 14. In about 1 year in 10 it comes after May 1, and in 9 years in 10 it comes after April 1.
When is the first frost in Decatur?
The first fall frost (32°F) usually arrives around October 24. There’s a 10% chance of a freeze by October 11 and a 90% chance by November 5.
Can it frost in Decatur 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 April 26.
What growing zone is Decatur?
Decatur is in USDA Plant Hardiness Zone 6a (average annual extreme minimum temperature −10 to −5°F), based on the 2023 USDA map for ZIP code 62523. See growing zones in Illinois.
More: all Illinois frost dates · Illinois growing zones · UV index today in Decatur · frost vs. freeze