When to plant in Riverton, WY
USDA Zone 5aRiverton, Wyoming frost dates, USDA zone, and a full-year planting calendar, drawn from the nearest NOAA station and tuned to the local season.
Zone 5a means Riverton sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
The average last spring frost in Riverton is now 5 days earlier than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
RIVERTON · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Riverton’s own odds, recorded at RIVERTON.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Jun 10 | May 28 | May 12 | Sep 3 | Sep 14 | Sep 27 |
| 32°F | May 26 | May 12 | May 1 | Sep 11 | Sep 24 | Oct 7 |
| 28°F | May 16 | May 1 | Apr 20 | Sep 21 | Oct 4 | Oct 17 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Riverton, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 32 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Riverton planting FAQ
When is the last spring frost in Riverton, WY?
Riverton's average last spring frost falls near May 12 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Riverton, WY?
In Riverton, the first 32°F freeze of fall lands around September 24 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Riverton in?
Riverton is in USDA hardiness zone 5a. In zone 5a, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Riverton?
There are roughly 135 frost-free days in Riverton (a short growing season), running from the average last frost around May 12 to the first fall frost near September 24.
When should I plant tomatoes in Riverton?
In Riverton, start tomato seeds indoors around March 17–March 31, then transplant seedlings outdoors around May 19 once the danger of frost has passed.
Never miss a window in Riverton
An email when it’s time to start seeds, transplant, and sow — timed to Riverton’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Casper · 169 km
- Rock Springs · 174 km
- Cody · 175 km
- Green River · 191 km
- Jackson · 200 km
- Sheridan · 227 km
- Gillette · 270 km
- Rexburg · 289 km
Frost dates recorded at RIVERTON, 1 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Riverton, WY — Frost Dates & Zone 5a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00487760. Retrieved from https://blissgarden.com/wyoming/riverton.