Arco, ID frost dates
Last spring frostMay 22median date
First fall frostSep 22median date
Growing season123 daysfrost-free
Hardiness zone5aZone 5a
How Arco compares
- In 8 years out of 10, the last spring frost in Arco falls between May 5 and June 9, a 35-day window. The first fall frost falls between September 4 and October 7.
- The median last frost is 8 days later than the Idaho median of May 14.
- Its 123-day growing season is longer than 22% of the 244 Idaho places with a regular frost season (state median 138 days).
- The last frost is 19 days later than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 192 nights a year at or below 32°F.
- Compared with Idaho Falls, ID, 107 km away, the last frost here is 13 days later than there and the growing season is 22 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 5 |
| 50% (median) | May 22 |
| 10% (safe for tender plants) | June 9 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 4 |
| 50% (median) | September 22 |
| 90% (late) | October 7 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Arco, ID
Arco, ID frost dates — last frost May 22, first frost Sep 22, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 27 to Mar 13Transplant outside: Apr 24 to May 8
Start indoors: Mar 13 to Mar 27Transplant outside: Jun 5 to Jun 19
Start indoors: Mar 13 to Mar 27Transplant outside: Jun 5 to Jun 19
Start indoors: Mar 27 to Apr 10Transplant outside: May 29 to Jun 12
Start indoors: Mar 27 to Apr 10Transplant outside: May 1 to May 15Sow outdoors: Apr 24 to May 29Plant for fall: Jul 28 to Aug 25
Start indoors: Mar 27 to Apr 10Transplant outside: Apr 24 to May 8Sow outdoors: Apr 24 to May 8Plant for fall: Jul 14 to Aug 4
Start indoors: Mar 27 to Apr 10Transplant outside: May 8 to May 22Plant for fall: Jun 16 to Jul 7
Start indoors: Mar 27 to Apr 10Transplant outside: May 1 to May 15Plant for fall: Jun 16 to Jul 7
Start indoors: Mar 27 to Apr 10Transplant outside: May 8 to May 22Plant for fall: Jun 16 to Jul 7
Start indoors: Apr 10 to Apr 24Transplant outside: Jun 12 to Jun 26Sow outdoors: Jun 12 to Jun 26
Start indoors: Apr 10 to Apr 24Transplant outside: May 29 to Jun 12
Sow outdoors: Apr 10 to May 1Plant for fall: Jun 30 to Jul 21
Sow outdoors: Apr 10 to May 1Plant for fall: Jul 28 to Aug 18
Sow outdoors: Apr 17 to May 29Plant for fall: Aug 11 to Sep 1
Start indoors: Apr 24 to May 1Transplant outside: Jun 5 to Jun 12Sow outdoors: May 29 to Jun 12Plant for fall: Jul 7 to Jul 21
Start indoors: Apr 24 to May 1Sow outdoors: May 29 to Jun 12Plant for fall: Jul 14 to Jul 28
Start indoors: Apr 24 to May 1Sow outdoors: May 29 to Jun 12
Start indoors: Apr 24 to May 1Transplant outside: Jun 5 to Jun 19
Sow outdoors: May 1 to May 29Plant for fall: Jun 30 to Jul 14
Sow outdoors: May 1 to May 29Plant for fall: Jul 14 to Jul 28
Sow outdoors: May 1 to May 22
Sow outdoors: May 8 to Jun 5Plant for fall: Jul 14 to Jul 28
Sow outdoors: May 8 to May 29Plant for fall: Jul 28 to Aug 18
Sow outdoors: May 29 to Jun 19Plant for fall: Jul 7 to Jul 21
Sow outdoors: May 29 to Jun 12
Transplant outside: Jun 5 to Jun 26
Plant for fall: Sep 8 to Oct 13
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Arco, ID
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 27 – Mar 13 | Apr 24 – May 8 | — | — |
| Peppers | Mar 13 – Mar 27 | Jun 5 – Jun 19 | — | — |
| Eggplant | Mar 13 – Mar 27 | Jun 5 – Jun 19 | — | — |
| Tomatoes | Mar 27 – Apr 10 | May 29 – Jun 12 | — | — |
| Lettuce | Mar 27 – Apr 10 | May 1 – May 15 | Apr 24 – May 29 | Jul 28 – Aug 25 |
| Kale | Mar 27 – Apr 10 | Apr 24 – May 8 | Apr 24 – May 8 | Jul 14 – Aug 4 |
| Broccoli | Mar 27 – Apr 10 | May 8 – May 22 | — | Jun 16 – Jul 7 |
| Cabbage | Mar 27 – Apr 10 | May 1 – May 15 | — | Jun 16 – Jul 7 |
| Cauliflower | Mar 27 – Apr 10 | May 8 – May 22 | — | Jun 16 – Jul 7 |
| Okra | Apr 10 – Apr 24 | Jun 12 – Jun 26 | Jun 12 – Jun 26 | — |
| Basil | Apr 10 – Apr 24 | May 29 – Jun 12 | — | — |
| Peas | — | — | Apr 10 – May 1 | Jun 30 – Jul 21 |
| Spinach | — | — | Apr 10 – May 1 | Jul 28 – Aug 18 |
| Radishes | — | — | Apr 17 – May 29 | Aug 11 – Sep 1 |
| Cucumbers | Apr 24 – May 1 | Jun 5 – Jun 12 | May 29 – Jun 12 | Jul 7 – Jul 21 |
| Zucchini & Summer Squash | Apr 24 – May 1 | — | May 29 – Jun 12 | Jul 14 – Jul 28 |
| Winter Squash & Pumpkins | Apr 24 – May 1 | — | May 29 – Jun 12 | — |
| Melons & Watermelon | Apr 24 – May 1 | Jun 5 – Jun 19 | — | — |
| Carrots | — | — | May 1 – May 29 | Jun 30 – Jul 14 |
| Beets | — | — | May 1 – May 29 | Jul 14 – Jul 28 |
| Potatoes | — | — | May 1 – May 22 | — |
| Swiss Chard | — | — | May 8 – Jun 5 | Jul 14 – Jul 28 |
| Cilantro | — | — | May 8 – May 29 | Jul 28 – Aug 18 |
| Green Beans | — | — | May 29 – Jun 19 | Jul 7 – Jul 21 |
| Sweet Corn | — | — | May 29 – Jun 12 | — |
| Sweet Potatoes | — | Jun 5 – Jun 26 | — | — |
| Garlic | — | — | — | Sep 8 – Oct 13 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Arco, ID weather station, about 1 km away (elevation 5,325 ft (1,623 m)).
Frost dates near Arco
- Moore May 22 · Sep 22
- Howe May 24 · Sep 14
- Mackay Jun 1 · Sep 20
- Atomic City Jun 11 · Sep 6
- Carey Jun 16 · Sep 9
- Monteview Jun 12 · Sep 7
- Picabo Jun 16 · Sep 9
- Terreton Jun 3 · Sep 11
- Bellevue May 13 · Oct 2
- Pingree May 20 · Sep 20
Frequently asked questions
When is the last frost in Arco, ID?
The median last spring frost in Arco, ID is May 22. There is still about a 10% chance of frost after June 9, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Arco, ID?
The median first fall frost is September 22, with about a 10% chance of frost before September 4.
How long is the growing season in Arco, ID?
About 123 days between the median last spring frost and first fall frost.
What planting zone is Arco, ID?
Arco, ID is in USDA hardiness zone 5a.