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Will it freeze in Riverton in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Tonight: 30°F (Thu, Nov 5, 6:00 PM MST to Fri, Nov 6, 6:00 AM MST).
Tonight: forecast low 30°F. Freeze.
NWS forecast period: Thu, Nov 5, 6:00 PM MST to Fri, Nov 6, 6:00 AM MST.
7 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 30°F Freeze · Mostly Cloudy
- Fri, Nov 6 28°F Hard freeze · Mostly Clear
- Sat, Nov 7 30°F Freeze · Mostly Clear
- Sun, Nov 8 33°F Frost possible · Partly Cloudy
- Mon, Nov 9 33°F Frost possible · Partly Cloudy
- Tue, Nov 10 32°F Freeze · Mostly Clear
- Wed, Nov 11 32°F Freeze · 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 Riverton
The median first fall hard-freeze date (28°F) is October 4, from NOAA’s 1991–2020 Climate Normals at Riverton. 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 | May 12 · May 28 · Jun 10 | Sep 3 · Sep 14 · Sep 27 | 109 days |
| 32°F freeze | May 1 · May 12 · May 26 | Sep 11 · Sep 24 · Oct 7 | 132 days |
| 28°F hard freeze | Apr 20 · May 1 · May 16 | Sep 21 · Oct 4 · Oct 17 | 154 days |
Average high temperature by month
1991–2020 normals at Riverton
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 Riverton, WY come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Riverton (station USC00487760, elevation 4,955 ft), 0.4 mi from Riverton. 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 Riverton
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Lander, WY | 22 mi | May 18 | Sep 27 |
| Rawlins, WY | 104 mi | May 17 | Oct 2 |
| Casper, WY | 105 mi | May 10 | Sep 29 |
| Rock Springs, WY | 108 mi | May 24 | Sep 24 |
| Cody, WY | 109 mi | May 12 | Oct 1 |
| Green River, WY | 119 mi | May 24 | Sep 22 |
| Powell, WY | 121 mi | May 19 | Sep 20 |
| Jackson, WY | 124 mi | Jun 20 | Aug 31 |
| Sheridan, WY | 141 mi | May 21 | Sep 23 |
| Douglas, WY | 152 mi | May 19 | Sep 23 |
Frequently asked questions
When is the last frost in Riverton?
On average, the last spring frost (32°F) in Riverton is around May 12. In about 1 year in 10 it comes after May 26, and in 9 years in 10 it comes after May 1.
When is the first frost in Riverton?
The first fall frost (32°F) usually arrives around September 24. There’s a 10% chance of a freeze by September 11 and a 90% chance by October 7.
Can it frost in Riverton 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 28.
What growing zone is Riverton?
Riverton 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 82501. See growing zones in Wyoming.
More: all Wyoming frost dates · Wyoming growing zones · frost vs. freeze