Frost Dates for Riverton, WY 82501
Last spring frost May 22 · First fall frost September 22 · 123 frost-free days · USDA Zone 5a
ZIP 82501 has about 19,400 people.
Moderate season: 123 frost-free days. Spring frost risk spans May 3–June 6 (34 days). Fall frost risk spans September 12–October 3 (21 days).
Frost probability for 82501
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | June 6 | May 22 | May 3 |
| Fall (first frost) | September 12 | September 22 | October 3 |
Dates come from NOAA 1971–2000 freeze probabilities at PAVILLION (43.1 km away); the 50% date is the median year.
Which crops fit a 123-day season in Riverton
In Riverton (123 frost-free days, a moderate season), 35 of 56 planner crops fit outright, 15 get two plantings, 5 need an indoor start, 1 crop is perennial.
| Crop | Start indoors | Plant out / sow | Days you have | Verdict | Last sow date |
|---|---|---|---|---|---|
| Tomato | Apr 17 | Jun 5–Jun 12 | 81 | fits: 80 days to maturity, 81 available after Jun 5. | — |
| Pepper | Apr 10 | Jun 5–Jun 12 | 81 | fits: 75 days to maturity, 81 available after Jun 5. | — |
| Lettuce | Mar 27 | Apr 24–May 1 | 158 | two-plantings: Plant Apr 24 and again by Aug 1; both mature before Sep 29. | Aug 1 |
| Carrots | — | May 1–May 8 | 165 | fits: 70 days to maturity, 165 available after May 1. | Jul 21 |
| Cucumber | May 1 | Jun 5–Jun 12 | 95 | fits: 60 days to maturity, 95 available after Jun 5. | Jun 26 |
| Beans | — | May 29–Jun 12 | 109 | fits: 60 days to maturity, 109 available after May 29. | Jul 3 |
| Peas | — | Mar 27–Jun 5 | 186 | fits: 65 days to maturity, 186 available after Mar 27. | Jul 12 |
| Zucchini | May 8 | Jun 5–Jun 12 | 95 | fits: 55 days to maturity, 95 available after Jun 5. | Jul 1 |
| Onion | Feb 27 | Apr 24–May 8 | 158 | fits: 100 days to maturity, 158 available after Apr 24. | — |
| Spinach | — | Mar 27–May 15 | 200 | two-plantings: Plant Mar 27 and again by Aug 20; both mature before Oct 13. | Aug 20 |
| Kale | Mar 13 | Apr 24–May 8 | 172 | two-plantings: Plant Apr 24 and again by Aug 5; both mature before Oct 13. | Aug 5 |
| Broccoli | Mar 27 | Apr 24–May 8 | 158 | fits: 80 days to maturity, 158 available after Apr 24. | Jun 27 |
| Cabbage | Mar 27 | Apr 24–May 8 | 172 | fits: 70 days to maturity, 172 available after Apr 24. | Jul 21 |
| Radish | — | Mar 27–Jun 19 | 186 | two-plantings: Plant Mar 27 and again by Aug 21; both mature before Sep 29. | Aug 21 |
| Beets | — | Mar 27–Jun 19 | 186 | two-plantings: Plant Mar 27 and again by Jul 22; both mature before Sep 29. | Jul 22 |
| Potatoes | — | May 8–May 15 | 144 | fits: 90 days to maturity, 144 available after May 8. | — |
| Garlic | — | Sep 22 | 228 | overwinter: Plant Sep 22 to Oct 13; harvest the following summer. | Oct 13 |
| Strawberry | — | Apr 17–Jun 12 | 179 | perennial: A perennial: plant Apr 17; it fruits from the following year and keeps producing for several years. | — |
| Corn | Apr 24 | May 29–Jun 5 | 95 | fits: 75 days to maturity, 95 available after May 29. | Jun 4 |
| Pumpkin | May 8 | Jun 5–Jun 5 | 88 | head-start: Even planted out Jun 5, the outdoor season is about 12 days short; choose an early variety or grow under cover. | — |
| Cauliflower | Apr 10 | May 15–May 29 | 137 | fits: 75 days to maturity, 137 available after May 15. | Jul 2 |
| Swiss Chard | Mar 27 | May 8–May 8 | 144 | two-plantings: Plant May 8 and again by Jul 22; both mature before Sep 29. | Jul 22 |
| Arugula | — | Mar 27–Jun 19 | 200 | two-plantings: Plant Mar 27 and again by Aug 20; both mature before Oct 13. | Aug 20 |
| Brussel Sprouts | Mar 27 | Apr 24–May 8 | 172 | fits: 100 days to maturity, 172 available after Apr 24. | Jun 21 |
| Butternut Squash | May 8 | Jun 5–Jun 12 | 88 | head-start: Even planted out Jun 5, the outdoor season is about 12 days short; choose an early variety or grow under cover. | — |
| Eggplant | Apr 3 | Jun 5–Jun 12 | 81 | fits: 70 days to maturity, 81 available after Jun 5. | — |
| Okra | Apr 24 | May 29–Jun 5 | 102 | fits: 55 days to maturity, 102 available after May 29. | Jul 1 |
| Basil | Apr 17 | Jun 12–Jun 12 | 88 | fits: 60 days to maturity, 88 available after Jun 12. | Jun 26 |
| Cilantro | — | Apr 24–May 15 | 158 | two-plantings: Plant Apr 24 and again by Jul 27; both mature before Sep 29. | Jul 27 |
| Parsley | Mar 13 | May 29–Jun 5 | 123 | fits: 70 days to maturity, 123 available after May 29. | Jul 7 |
| Celery | Mar 13 | May 29–Jun 12 | 123 | fits: 120 days to maturity, 123 available after May 29. | — |
| Scallions | Mar 13 | Apr 24–May 8 | 172 | two-plantings: Plant Apr 24 and again by Jul 31; both mature before Oct 13. | Jul 31 |
| Turnip | — | Apr 24–May 8 | 172 | two-plantings: Plant Apr 24 and again by Aug 10; both mature before Oct 13. | Aug 10 |
| Kohlrabi | — | Apr 10–Apr 24 | 186 | two-plantings: Plant Apr 10 and again by Aug 5; both mature before Oct 13. | Aug 5 |
| Bok Choy | Apr 24 | May 15–May 22 | 137 | two-plantings: Plant May 15 and again by Aug 1; both mature before Sep 29. | Aug 1 |
| Collards | Mar 13 | Apr 24–May 8 | 172 | two-plantings: Plant Apr 24 and again by Jul 31; both mature before Oct 13. | Jul 31 |
| Cantaloupe | May 8 | Jun 5–Jun 12 | 81 | head-start: Even planted out Jun 5, the outdoor season is about 4 days short; choose an early variety or grow under cover. | — |
| Chives | Feb 27 | May 29–Jun 5 | 137 | fits: 90 days to maturity, 137 available after May 29. | — |
| Dill | — | Mar 27–Jun 19 | 186 | two-plantings: Plant Mar 27 and again by Jul 22; both mature before Sep 29. | Jul 22 |
| Oregano | Mar 13 | May 29–Jun 5 | 137 | fits: 80 days to maturity, 137 available after May 29. | — |
| Rosemary | Feb 27 | May 29–Jun 5 | 123 | fits: 80 days to maturity, 123 available after May 29. | — |
| Sage | Mar 27 | May 29–Jun 5 | 137 | fits: 75 days to maturity, 137 available after May 29. | — |
| Thyme | Mar 13 | May 29–Jun 5 | 137 | fits: 90 days to maturity, 137 available after May 29. | — |
| Calendula | Apr 10 | May 8–May 22 | 144 | two-plantings: Plant May 8 and again by Jul 27; both mature before Sep 29. | Jul 27 |
| Cosmos | Apr 24 | May 22–Jun 5 | 109 | fits: 60 days to maturity, 109 available after May 22. | Jun 26 |
| Lavender | Feb 27 | May 22–Jun 5 | 144 | fits: 90 days to maturity, 144 available after May 22. | — |
| Marigolds | Apr 10 | May 22–May 29 | 109 | fits: 50 days to maturity, 109 available after May 22. | Jul 6 |
| Melons | May 8 | Jun 5–Jun 12 | 81 | head-start: Even planted out Jun 5, the outdoor season is about 4 days short; choose an early variety or grow under cover. | — |
| Mint | — | May 22–Jun 5 | 144 | fits: 90 days to maturity, 144 available after May 22. | — |
| Nasturtiums | Apr 24 | May 22–May 29 | 109 | fits: 55 days to maturity, 109 available after May 22. | Jul 1 |
| Pole Beans | — | May 29–Jun 12 | 102 | fits: 65 days to maturity, 102 available after May 29. | Jun 21 |
| Spaghetti Squash | May 8 | Jun 5–Jun 12 | 88 | head-start: Even planted out Jun 5, the outdoor season is about 2 days short; choose an early variety or grow under cover. | — |
| Sunflowers | — | May 22–Jun 5 | 109 | fits: 70 days to maturity, 109 available after May 22. | Jun 16 |
| Tomatillos | Mar 27 | May 29–Jun 5 | 88 | fits: 75 days to maturity, 88 available after May 29. | — |
| Watermelon | May 8 | May 29–Jun 5 | 88 | fits: 80 days to maturity, 88 available after May 29. | — |
| Yellow Squash | May 8 | Jun 5–Jun 12 | 95 | fits: 55 days to maturity, 95 available after Jun 5. | Jul 1 |
| Zinnias | Apr 24 | May 22–Jun 5 | 109 | fits: 60 days to maturity, 109 available after May 22. | Jun 26 |
Month by month in Riverton
| Month | What to do |
|---|---|
| January | Plan your garden layout and order seeds. Research varieties suited to your frost dates. |
| February | Start indoors: Chives (Feb 27), Lavender (Feb 27), Onion (Feb 27), Rosemary (Feb 27). |
| March | Start indoors: Celery (Mar 13), Collards (Mar 13), Kale (Mar 13), Oregano (Mar 13), Parsley (Mar 13), Scallions (Mar 13), +8 more. Direct sow from: Arugula (Mar 27), Beets (Mar 27), Dill (Mar 27), Peas (Mar 27), Radish (Mar 27), Spinach (Mar 27). |
| April | Start indoors: Eggplant (Apr 3), Calendula (Apr 10), Cauliflower (Apr 10), Marigolds (Apr 10), Pepper (Apr 10), Basil (Apr 17), +7 more. Direct sow from: Kohlrabi (Apr 10), Cilantro (Apr 24), Turnip (Apr 24). Transplant from: Broccoli (Apr 24), Brussel Sprouts (Apr 24), Cabbage (Apr 24), Collards (Apr 24), Kale (Apr 24), Lettuce (Apr 24), +2 more. Plant: Strawberry (Apr 17). |
| May | Start indoors: Cucumber (May 1), Butternut Squash (May 8), Cantaloupe (May 8), Melons (May 8), Pumpkin (May 8), Spaghetti Squash (May 8), +3 more. Direct sow from: Carrots (May 1), Potatoes (May 8), Sunflowers (May 22), Beans (May 29), Pole Beans (May 29). Transplant from: Calendula (May 8), Swiss Chard (May 8), Bok Choy (May 15), Cauliflower (May 15), Cosmos (May 22), Lavender (May 22), +15 more. Last frost around May 22. |
| June | Transplant from: Butternut Squash (Jun 5), Cantaloupe (Jun 5), Cucumber (Jun 5), Eggplant (Jun 5), Melons (Jun 5), Pepper (Jun 5), +6 more. Last sowing dates: Corn (Jun 4), Sunflowers (Jun 16), Brussel Sprouts (Jun 21), Pole Beans (Jun 21), Basil (Jun 26), Cosmos (Jun 26), +3 more. |
| July | Last sowing dates: Nasturtiums (Jul 1), Okra (Jul 1), Yellow Squash (Jul 1), Zucchini (Jul 1), Cauliflower (Jul 2), Beans (Jul 3), +12 more. |
| August | Last sowing dates: Bok Choy (Aug 1), Lettuce (Aug 1), Kale (Aug 5), Kohlrabi (Aug 5), Turnip (Aug 10), Arugula (Aug 20), +2 more. |
| September | Direct sow from: Garlic (Sep 22). First frost around September 22. |
| October | Last sowing dates: Garlic (Oct 13). |
| November | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
| December | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
Frequently Asked Questions
What is the last frost date for Riverton, WY (ZIP 82501)?
The median last spring frost date for Riverton, WY (ZIP code 82501) is around May 22. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area. One year in ten frost ends before May 3; one in ten it runs past June 6.
What is the first fall frost date in Riverton, WY?
The median first fall frost date for Riverton, WY is around September 22. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses. The first frost arrives around September 12 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Riverton, WY?
The frost-free growing season in Riverton is about 123 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side. In Riverton (123 frost-free days, a moderate season), 35 of 56 planner crops fit outright, 15 get two plantings, 5 need an indoor start, 1 crop is perennial.
What USDA hardiness zone is Riverton, WY?
Riverton, WY is in USDA hardiness zone 5a (2023 USDA Plant Hardiness Zone Map). Zones come from the average coldest winter temperature, so they tell you which perennials survive the winter; the frost dates on this page tell you when to plant.
When should I start tomatoes indoors in Riverton, WY?
Start tomatoes indoors Apr 17 and plant out Jun 5 in Riverton. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Riverton?
Two: plant Apr 24 and again by Aug 1; both mature before Sep 29.
When do I plant garlic in Riverton?
Sep 22 to Oct 13; it overwinters and is ready the following summer.
Can I grow Butternut Squash in Riverton?
Yes, with help. Even planted out Jun 5, the outdoor season is about 12 days short; choose an early variety or grow under cover.
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