Idaho City, ID frost dates
Last spring frostJun 17median date
First fall frostSep 5median date
Growing season80 daysfrost-free
Hardiness zone6bZone 6b
How Idaho City compares
- In 8 years out of 10, the last spring frost in Idaho City falls between May 30 and July 4, a 35-day window. The first fall frost falls between August 23 and September 21.
- The median last frost is 34 days later than the Idaho median of May 14.
- Its 80-day growing season is among the shortest of the 244 Idaho places with a regular frost season.
- The last frost is 56 days later than the zone 6b median of Apr 22. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6b chart.
- The weather station records an average of 224 nights a year at or below 32°F.
- Compared with Boise, ID, 57 km away, the last frost here is 54 days later than there and the growing season is 100 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 30 |
| 50% (median) | June 17 |
| 10% (safe for tender plants) | July 4 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | August 23 |
| 50% (median) | September 5 |
| 90% (late) | September 21 |
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 Idaho City, ID
Idaho City, ID frost dates — last frost Jun 17, first frost Sep 5, zone 6b. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Mar 25 to Apr 8Transplant outside: May 20 to Jun 3
Start indoors: Apr 8 to Apr 22Transplant outside: Jul 1 to Jul 15
Start indoors: Apr 8 to Apr 22Transplant outside: Jul 1 to Jul 15
Start indoors: Apr 22 to May 6Transplant outside: Jun 24 to Jul 8
Start indoors: Apr 22 to May 6Transplant outside: May 27 to Jun 10Sow outdoors: May 20 to Jun 24Plant for fall: Jul 11 to Aug 8
Start indoors: Apr 22 to May 6Transplant outside: May 20 to Jun 3Sow outdoors: May 20 to Jun 3
Start indoors: Apr 22 to May 6Transplant outside: Jun 3 to Jun 17
Start indoors: Apr 22 to May 6Transplant outside: May 27 to Jun 10
Start indoors: Apr 22 to May 6Transplant outside: Jun 3 to Jun 17
Start indoors: May 6 to May 20Transplant outside: Jul 8 to Jul 22Sow outdoors: Jul 8 to Jul 22
Start indoors: May 6 to May 20Transplant outside: Jun 24 to Jul 8
Sow outdoors: May 6 to May 27
Sow outdoors: May 6 to May 27Plant for fall: Jul 11 to Aug 1
Sow outdoors: May 13 to Jun 24Plant for fall: Jul 25 to Aug 15
Start indoors: May 20 to May 27Transplant outside: Jul 1 to Jul 8Sow outdoors: Jun 24 to Jul 8
Start indoors: May 20 to May 27Sow outdoors: Jun 24 to Jul 8
Start indoors: May 20 to May 27Sow outdoors: Jun 24 to Jul 8
Start indoors: May 20 to May 27Transplant outside: Jul 1 to Jul 15
Sow outdoors: May 27 to Jun 24
Sow outdoors: May 27 to Jun 24
Sow outdoors: May 27 to Jun 17
Sow outdoors: Jun 3 to Jul 1
Sow outdoors: Jun 3 to Jun 24Plant for fall: Jul 11 to Aug 1
Sow outdoors: Jun 24 to Jul 15
Sow outdoors: Jun 24 to Jul 8
Transplant outside: Jul 1 to Jul 22
Plant for fall: Aug 22 to Sep 26
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Idaho City, ID
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 25 – Apr 8 | May 20 – Jun 3 | — | — |
| Peppers Warning: Your frost-free season is about 80 days, which is tight for peppers (75+ days). Choose early varieties and use transplants or row covers. | Apr 8 – Apr 22 | Jul 1 – Jul 15 | — | — |
| Eggplant Warning: Your frost-free season is about 80 days, which is tight for eggplant (75+ days). Choose early varieties and use transplants or row covers. | Apr 8 – Apr 22 | Jul 1 – Jul 15 | — | — |
| Tomatoes Warning: Your frost-free season is about 80 days, which is tight for tomatoes (70+ days). Choose early varieties and use transplants or row covers. | Apr 22 – May 6 | Jun 24 – Jul 8 | — | — |
| Lettuce | Apr 22 – May 6 | May 27 – Jun 10 | May 20 – Jun 24 | Jul 11 – Aug 8 |
| Kale | Apr 22 – May 6 | May 20 – Jun 3 | May 20 – Jun 3 | — |
| Broccoli | Apr 22 – May 6 | Jun 3 – Jun 17 | — | — |
| Cabbage | Apr 22 – May 6 | May 27 – Jun 10 | — | — |
| Cauliflower | Apr 22 – May 6 | Jun 3 – Jun 17 | — | — |
| Okra | May 6 – May 20 | Jul 8 – Jul 22 | Jul 8 – Jul 22 | — |
| Basil | May 6 – May 20 | Jun 24 – Jul 8 | — | — |
| Peas | — | — | May 6 – May 27 | — |
| Spinach | — | — | May 6 – May 27 | Jul 11 – Aug 1 |
| Radishes | — | — | May 13 – Jun 24 | Jul 25 – Aug 15 |
| Cucumbers | May 20 – May 27 | Jul 1 – Jul 8 | Jun 24 – Jul 8 | — |
| Zucchini & Summer Squash | May 20 – May 27 | — | Jun 24 – Jul 8 | — |
| Winter Squash & Pumpkins Warning: Your frost-free season is about 80 days, which is tight for winter squash & pumpkins (100+ days). Choose early varieties and use transplants or row covers. | May 20 – May 27 | — | Jun 24 – Jul 8 | — |
| Melons & Watermelon Warning: Your frost-free season is about 80 days, which is tight for melons & watermelon (85+ days). Choose early varieties and use transplants or row covers. | May 20 – May 27 | Jul 1 – Jul 15 | — | — |
| Carrots | — | — | May 27 – Jun 24 | — |
| Beets | — | — | May 27 – Jun 24 | — |
| Potatoes | — | — | May 27 – Jun 17 | — |
| Swiss Chard | — | — | Jun 3 – Jul 1 | — |
| Cilantro | — | — | Jun 3 – Jun 24 | Jul 11 – Aug 1 |
| Green Beans | — | — | Jun 24 – Jul 15 | — |
| Sweet Corn Warning: Your frost-free season is about 80 days, which is tight for sweet corn (80+ days). Choose early varieties and use transplants or row covers. | — | — | Jun 24 – Jul 8 | — |
| Sweet Potatoes Warning: Your frost-free season is about 80 days, which is tight for sweet potatoes (100+ days). Choose early varieties and use transplants or row covers. | — | Jul 1 – Jul 22 | — | — |
| Garlic | — | — | — | Aug 22 – Sep 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 Idaho City, ID weather station, 11 km away (elevation 3,967 ft (1,209 m)).
Frost dates near Idaho City
- Placerville Jun 1 · Sep 10
- Garden Valley Jun 1 · Sep 10
- Lowman Jun 6 · Sep 4
- Atlanta Jun 6 · Sep 4
- Horseshoe Bend May 17 · Oct 12
- Banks Jun 1 · Sep 10
- Garden City May 17 · Oct 12
- Sweet Apr 30 · Oct 17
- Eagle May 17 · Oct 12
- Mountain Home Afb Apr 30 · Oct 17
Frequently asked questions
When is the last frost in Idaho City, ID?
The median last spring frost in Idaho City, ID is June 17. There is still about a 10% chance of frost after July 4, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Idaho City, ID?
The median first fall frost is September 5, with about a 10% chance of frost before August 23.
How long is the growing season in Idaho City, ID?
About 80 days between the median last spring frost and first fall frost.
What planting zone is Idaho City, ID?
Idaho City, ID is in USDA hardiness zone 6b.