Roberts, ID frost dates
Last spring frostMay 9median date
First fall frostOct 5median date
Growing season149 daysfrost-free
Hardiness zone5aZone 5a
How Roberts compares
- In 8 years out of 10, the last spring frost in Roberts falls between April 27 and May 25, a 28-day window. The first fall frost falls between September 21 and October 18.
- The median last frost is 5 days earlier than the Idaho median of May 14.
- Its 149-day growing season is longer than 62% of the 244 Idaho places with a regular frost season (state median 138 days).
- The last frost is 6 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 163 nights a year at or below 32°F.
- Compared with Idaho Falls, ID, 27 km away, the last frost here is the same as there and the growing season is 4 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 27 |
| 50% (median) | May 9 |
| 10% (safe for tender plants) | May 25 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 21 |
| 50% (median) | October 5 |
| 90% (late) | October 18 |
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 Roberts, ID
Roberts, ID frost dates — last frost May 9, first frost Oct 5, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 14 to Feb 28Transplant outside: Apr 11 to Apr 25
Start indoors: Feb 28 to Mar 14Transplant outside: May 23 to Jun 6
Start indoors: Feb 28 to Mar 14Transplant outside: May 23 to Jun 6
Start indoors: Mar 14 to Mar 28Transplant outside: May 16 to May 30
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 18 to May 2Sow outdoors: Apr 11 to May 16Plant for fall: Aug 10 to Sep 7
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 11 to Apr 25Sow outdoors: Apr 11 to Apr 25Plant for fall: Jul 27 to Aug 17
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 25 to May 9Plant for fall: Jun 29 to Jul 20
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 18 to May 2Plant for fall: Jun 29 to Jul 20
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 25 to May 9Plant for fall: Jun 29 to Jul 20
Start indoors: Mar 28 to Apr 11Transplant outside: May 30 to Jun 13Sow outdoors: May 30 to Jun 13
Start indoors: Mar 28 to Apr 11Transplant outside: May 16 to May 30
Sow outdoors: Mar 28 to Apr 18Plant for fall: Jul 13 to Aug 3
Sow outdoors: Mar 28 to Apr 18Plant for fall: Aug 10 to Aug 31
Sow outdoors: Apr 4 to May 16Plant for fall: Aug 24 to Sep 14
Start indoors: Apr 11 to Apr 18Transplant outside: May 23 to May 30Sow outdoors: May 16 to May 30Plant for fall: Jul 20 to Aug 3
Start indoors: Apr 11 to Apr 18Sow outdoors: May 16 to May 30Plant for fall: Jul 27 to Aug 10
Start indoors: Apr 11 to Apr 18Sow outdoors: May 16 to May 30
Start indoors: Apr 11 to Apr 18Transplant outside: May 23 to Jun 6
Sow outdoors: Apr 18 to May 16Plant for fall: Jul 13 to Jul 27
Sow outdoors: Apr 18 to May 16Plant for fall: Jul 27 to Aug 10
Sow outdoors: Apr 18 to May 9
Sow outdoors: Apr 25 to May 23Plant for fall: Jul 27 to Aug 10
Sow outdoors: Apr 25 to May 16Plant for fall: Aug 10 to Aug 31
Sow outdoors: May 16 to Jun 6Plant for fall: Jul 20 to Aug 3
Sow outdoors: May 16 to May 30
Transplant outside: May 23 to Jun 13
Plant for fall: Sep 21 to Oct 26
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Roberts, ID
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 14 – Feb 28 | Apr 11 – Apr 25 | — | — |
| Peppers | Feb 28 – Mar 14 | May 23 – Jun 6 | — | — |
| Eggplant | Feb 28 – Mar 14 | May 23 – Jun 6 | — | — |
| Tomatoes | Mar 14 – Mar 28 | May 16 – May 30 | — | — |
| Lettuce | Mar 14 – Mar 28 | Apr 18 – May 2 | Apr 11 – May 16 | Aug 10 – Sep 7 |
| Kale | Mar 14 – Mar 28 | Apr 11 – Apr 25 | Apr 11 – Apr 25 | Jul 27 – Aug 17 |
| Broccoli | Mar 14 – Mar 28 | Apr 25 – May 9 | — | Jun 29 – Jul 20 |
| Cabbage | Mar 14 – Mar 28 | Apr 18 – May 2 | — | Jun 29 – Jul 20 |
| Cauliflower | Mar 14 – Mar 28 | Apr 25 – May 9 | — | Jun 29 – Jul 20 |
| Okra | Mar 28 – Apr 11 | May 30 – Jun 13 | May 30 – Jun 13 | — |
| Basil | Mar 28 – Apr 11 | May 16 – May 30 | — | — |
| Peas | — | — | Mar 28 – Apr 18 | Jul 13 – Aug 3 |
| Spinach | — | — | Mar 28 – Apr 18 | Aug 10 – Aug 31 |
| Radishes | — | — | Apr 4 – May 16 | Aug 24 – Sep 14 |
| Cucumbers | Apr 11 – Apr 18 | May 23 – May 30 | May 16 – May 30 | Jul 20 – Aug 3 |
| Zucchini & Summer Squash | Apr 11 – Apr 18 | — | May 16 – May 30 | Jul 27 – Aug 10 |
| Winter Squash & Pumpkins | Apr 11 – Apr 18 | — | May 16 – May 30 | — |
| Melons & Watermelon | Apr 11 – Apr 18 | May 23 – Jun 6 | — | — |
| Carrots | — | — | Apr 18 – May 16 | Jul 13 – Jul 27 |
| Beets | — | — | Apr 18 – May 16 | Jul 27 – Aug 10 |
| Potatoes | — | — | Apr 18 – May 9 | — |
| Swiss Chard | — | — | Apr 25 – May 23 | Jul 27 – Aug 10 |
| Cilantro | — | — | Apr 25 – May 16 | Aug 10 – Aug 31 |
| Green Beans | — | — | May 16 – Jun 6 | Jul 20 – Aug 3 |
| Sweet Corn | — | — | May 16 – May 30 | — |
| Sweet Potatoes | — | May 23 – Jun 13 | — | — |
| Garlic | — | — | — | Sep 21 – Oct 26 |
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 Rigby, ID weather station, 17 km away (elevation 4,856 ft (1,480 m)).
Frost dates near Roberts
- Lewisville May 9 · Oct 5
- Menan May 9 · Oct 5
- Rigby May 9 · Oct 5
- Ucon May 9 · Oct 5
- Hamer Jun 3 · Sep 11
- Iona May 9 · Oct 1
- Idaho Falls May 9 · Oct 1
- Terreton Jun 3 · Sep 11
- Rexburg May 12 · Sep 24
- Shelley May 23 · Sep 20
Frequently asked questions
When is the last frost in Roberts, ID?
The median last spring frost in Roberts, ID is May 9. There is still about a 10% chance of frost after May 25, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Roberts, ID?
The median first fall frost is October 5, with about a 10% chance of frost before September 21.
How long is the growing season in Roberts, ID?
About 149 days between the median last spring frost and first fall frost.
What planting zone is Roberts, ID?
Roberts, ID is in USDA hardiness zone 5a.