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Will it freeze in Poplar Grove 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 35°F. Frost possible.
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 35°F Frost possible · Patchy Drizzle then Mostly Cloudy
- Fri, Nov 6 26°F Hard freeze · Mostly Clear
- Sat, Nov 7 31°F Freeze · Mostly Clear
- Sun, Nov 8 32°F Freeze · Mostly Clear
- Mon, Nov 9 38°F Above 36°F · Mostly Clear
- Tue, Nov 10 36°F Frost possible · Partly Cloudy
- Wed, Nov 11 36°F Frost possible · 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 Poplar Grove
The median first fall hard-freeze date (28°F) is October 25, from NOAA’s 1991–2020 Climate Normals at Marengo. 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 26 · May 10 · May 26 | Sep 21 · Oct 3 · Oct 16 | 145 days |
| 32°F freeze | Apr 15 · Apr 28 · May 14 | Sep 28 · Oct 12 · Oct 27 | 166 days |
| 28°F hard freeze | Apr 3 · Apr 18 · May 4 | Oct 7 · Oct 25 · Nov 6 | 188 days |
Average high temperature by month
1991–2020 normals at Marengo
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 Poplar Grove, IL come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Marengo (station USC00115326, elevation 815 ft), 13 mi from Poplar Grove. 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 Poplar Grove
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Belvidere, IL | 6.2 mi | Apr 24 | Oct 17 |
| Loves Park, IL | 8.1 mi | Apr 24 | Oct 17 |
| Machesney Park, IL | 9.3 mi | May 1 | Oct 12 |
| Roscoe, IL | 9.9 mi | May 1 | Oct 12 |
| Harvard, IL | 12 mi | Apr 28 | Oct 12 |
| Rockford, IL | 13 mi | Apr 24 | Oct 17 |
| Rockton, IL | 13 mi | May 1 | Oct 12 |
| South Beloit, IL | 13 mi | May 1 | Oct 12 |
| Marengo, IL | 14 mi | Apr 28 | Oct 12 |
| Beloit, WI | 15 mi | May 1 | Oct 12 |
Frequently asked questions
When is the last frost in Poplar Grove?
On average, the last spring frost (32°F) in Poplar Grove is around April 28. In about 1 year in 10 it comes after May 14, and in 9 years in 10 it comes after April 15.
When is the first frost in Poplar Grove?
The first fall frost (32°F) usually arrives around October 12. There’s a 10% chance of a freeze by September 28 and a 90% chance by October 27.
Can it frost in Poplar Grove 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 10.
What growing zone is Poplar Grove?
Poplar Grove is in USDA Plant Hardiness Zone 5b (average annual extreme minimum temperature −15 to −10°F), based on the 2023 USDA map for ZIP code 61065. See growing zones in Illinois.
More: all Illinois frost dates · Illinois growing zones · frost vs. freeze