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Will it freeze in Portage in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Fri, Nov 6: 25°F (Fri, Nov 6, 6:00 PM CST to Sat, Nov 7, 6:00 AM CST).
Tonight: forecast low 34°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 34°F Frost possible · Mostly Cloudy
- Fri, Nov 6 25°F Hard freeze · Mostly Clear
- Sat, Nov 7 32°F Freeze · Partly Cloudy
- Sun, Nov 8 33°F Frost possible · Mostly Clear
- Mon, Nov 9 39°F Above 36°F · Mostly Clear
- Tue, Nov 10 35°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 Portage
The median first fall hard-freeze date (28°F) is October 22, from NOAA’s 1991–2020 Climate Normals at Portage Wastewater 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 26 · May 8 · May 24 | Sep 17 · Sep 30 · Oct 11 | 145 days |
| 32°F freeze | Apr 14 · Apr 28 · May 12 | Sep 26 · Oct 10 · Oct 23 | 164 days |
| 28°F hard freeze | Apr 4 · Apr 16 · Apr 30 | Oct 6 · Oct 22 · Nov 4 | 188 days |
Average high temperature by month
1991–2020 normals at Portage Wastewater 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 Portage, WI come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Portage Wastewater Plant (station USC00476718, elevation 785 ft), 1.9 mi from Portage. 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 Portage
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Baraboo, WI | 15 mi | May 5 | Oct 5 |
| DeForest, WI | 23 mi | May 4 | Oct 6 |
| Windsor, WI | 23 mi | May 4 | Oct 6 |
| Waunakee, WI | 25 mi | May 1 | Oct 10 |
| Columbus, WI | 26 mi | Apr 30 | Oct 9 |
| Reedsburg, WI | 27 mi | May 2 | Oct 7 |
| Sun Prairie, WI | 28 mi | May 1 | Oct 10 |
| Middleton, WI | 30 mi | Apr 28 | Oct 15 |
| Madison, WI | 32 mi | May 1 | Oct 9 |
| Beaver Dam, WI | 32 mi | May 2 | Oct 9 |
Frequently asked questions
When is the last frost in Portage?
On average, the last spring frost (32°F) in Portage is around April 28. In about 1 year in 10 it comes after May 12, and in 9 years in 10 it comes after April 14.
When is the first frost in Portage?
The first fall frost (32°F) usually arrives around October 10. There’s a 10% chance of a freeze by September 26 and a 90% chance by October 23.
Can it frost in Portage 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 8.
What growing zone is Portage?
Portage 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 53901. See growing zones in Wisconsin.
More: all Wisconsin frost dates · Wisconsin growing zones · frost vs. freeze