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Will it freeze in Knoxville in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Fri, Nov 6: 29°F (Fri, Nov 6, 6:00 PM CST to Sat, Nov 7, 6:00 AM CST).
Tonight: forecast low 38°F. Above 36°F.
NWS forecast period: Thu, Nov 5, 6:00 PM CST to Fri, Nov 6, 6:00 AM CST.
2 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 38°F Above 36°F · Mostly Cloudy
- Fri, Nov 6 29°F Freeze · Partly Cloudy
- Sat, Nov 7 36°F Frost possible · Mostly Clear
- Sun, Nov 8 38°F Above 36°F · Clear
- Mon, Nov 9 42°F Above 36°F · Clear
- Tue, Nov 10 41°F Above 36°F · Partly Cloudy
- Wed, Nov 11 42°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 Knoxville
The median first fall hard-freeze date (28°F) is October 29, from NOAA’s 1991–2020 Climate Normals at Knoxville. 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 15 · Apr 30 · May 12 | Sep 23 · Oct 7 · Oct 21 | 159 days |
| 32°F freeze | Apr 6 · Apr 20 · May 4 | Oct 1 · Oct 19 · Nov 1 | 180 days |
| 28°F hard freeze | Mar 28 · Apr 10 · Apr 24 | Oct 14 · Oct 29 · Nov 9 | 199 days |
Average high temperature by month
1991–2020 normals at Knoxville
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 Knoxville, IA come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Knoxville (station USC00134502, elevation 895 ft), 0.4 mi from Knoxville. 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 Knoxville
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Pella, IA | 11 mi | Apr 20 | Oct 19 |
| Oskaloosa, IA | 24 mi | Apr 21 | Oct 16 |
| Indianola, IA | 24 mi | Apr 24 | Oct 12 |
| Newton, IA | 26 mi | Apr 22 | Oct 17 |
| Pleasant Hill, IA | 29 mi | Apr 18 | Oct 20 |
| Altoona, IA | 30 mi | Apr 23 | Oct 15 |
| Des Moines, IA | 32 mi | Apr 18 | Oct 20 |
| Bondurant, IA | 32 mi | Apr 23 | Oct 15 |
| Norwalk, IA | 33 mi | Apr 18 | Oct 20 |
| Grinnell, IA | 35 mi | May 3 | Oct 6 |
Frequently asked questions
When is the last frost in Knoxville?
On average, the last spring frost (32°F) in Knoxville is around April 20. In about 1 year in 10 it comes after May 4, and in 9 years in 10 it comes after April 6.
When is the first frost in Knoxville?
The first fall frost (32°F) usually arrives around October 19. There’s a 10% chance of a freeze by October 1 and a 90% chance by November 1.
Can it frost in Knoxville 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 30.
What growing zone is Knoxville?
Knoxville 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 50138. See growing zones in Iowa.
More: all Iowa frost dates · Iowa growing zones · frost vs. freeze