Mackay, ID frost dates
Last spring frostJun 1median date
First fall frostSep 20median date
Growing season111 daysfrost-free
Hardiness zone5aZone 5a
How Mackay compares
- In 8 years out of 10, the last spring frost in Mackay falls between May 13 and June 21, a 39-day window. The first fall frost falls between September 4 and October 3.
- The median last frost is 18 days later than the Idaho median of May 14.
- Its 111-day growing season is longer than 17% of the 244 Idaho places with a regular frost season (state median 138 days).
- The last frost is 29 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 202 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 13 |
| 50% (median) | June 1 |
| 10% (safe for tender plants) | June 21 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 4 |
| 50% (median) | September 20 |
| 90% (late) | October 3 |
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 Mackay, ID
Mackay, ID frost dates — last frost Jun 1, first frost Sep 20, zone 5a. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Mar 9 to Mar 23Transplant outside: May 4 to May 18
Start indoors: Mar 23 to Apr 6Transplant outside: Jun 15 to Jun 29
Start indoors: Mar 23 to Apr 6Transplant outside: Jun 15 to Jun 29
Start indoors: Apr 6 to Apr 20Transplant outside: Jun 8 to Jun 22
Start indoors: Apr 6 to Apr 20Transplant outside: May 11 to May 25Sow outdoors: May 4 to Jun 8Plant for fall: Jul 26 to Aug 23
Start indoors: Apr 6 to Apr 20Transplant outside: May 4 to May 18Sow outdoors: May 4 to May 18Plant for fall: Jul 12 to Aug 2
Start indoors: Apr 6 to Apr 20Transplant outside: May 18 to Jun 1
Start indoors: Apr 6 to Apr 20Transplant outside: May 11 to May 25
Start indoors: Apr 6 to Apr 20Transplant outside: May 18 to Jun 1
Start indoors: Apr 20 to May 4Transplant outside: Jun 22 to Jul 6Sow outdoors: Jun 22 to Jul 6
Start indoors: Apr 20 to May 4Transplant outside: Jun 8 to Jun 22
Sow outdoors: Apr 20 to May 11Plant for fall: Jun 28 to Jul 19
Sow outdoors: Apr 20 to May 11Plant for fall: Jul 26 to Aug 16
Sow outdoors: Apr 27 to Jun 8Plant for fall: Aug 9 to Aug 30
Start indoors: May 4 to May 11Transplant outside: Jun 15 to Jun 22Sow outdoors: Jun 8 to Jun 22
Start indoors: May 4 to May 11Sow outdoors: Jun 8 to Jun 22Plant for fall: Jul 12 to Jul 26
Start indoors: May 4 to May 11Sow outdoors: Jun 8 to Jun 22
Start indoors: May 4 to May 11Transplant outside: Jun 15 to Jun 29
Sow outdoors: May 11 to Jun 8Plant for fall: Jun 28 to Jul 12
Sow outdoors: May 11 to Jun 8Plant for fall: Jul 12 to Jul 26
Sow outdoors: May 11 to Jun 1
Sow outdoors: May 18 to Jun 15Plant for fall: Jul 12 to Jul 26
Sow outdoors: May 18 to Jun 8Plant for fall: Jul 26 to Aug 16
Sow outdoors: Jun 8 to Jun 29
Sow outdoors: Jun 8 to Jun 22
Transplant outside: Jun 15 to Jul 6
Plant for fall: Sep 6 to Oct 11
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Mackay, ID
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 9 – Mar 23 | May 4 – May 18 | — | — |
| Peppers | Mar 23 – Apr 6 | Jun 15 – Jun 29 | — | — |
| Eggplant | Mar 23 – Apr 6 | Jun 15 – Jun 29 | — | — |
| Tomatoes | Apr 6 – Apr 20 | Jun 8 – Jun 22 | — | — |
| Lettuce | Apr 6 – Apr 20 | May 11 – May 25 | May 4 – Jun 8 | Jul 26 – Aug 23 |
| Kale | Apr 6 – Apr 20 | May 4 – May 18 | May 4 – May 18 | Jul 12 – Aug 2 |
| Broccoli | Apr 6 – Apr 20 | May 18 – Jun 1 | — | — |
| Cabbage | Apr 6 – Apr 20 | May 11 – May 25 | — | — |
| Cauliflower | Apr 6 – Apr 20 | May 18 – Jun 1 | — | — |
| Okra | Apr 20 – May 4 | Jun 22 – Jul 6 | Jun 22 – Jul 6 | — |
| Basil | Apr 20 – May 4 | Jun 8 – Jun 22 | — | — |
| Peas | — | — | Apr 20 – May 11 | Jun 28 – Jul 19 |
| Spinach | — | — | Apr 20 – May 11 | Jul 26 – Aug 16 |
| Radishes | — | — | Apr 27 – Jun 8 | Aug 9 – Aug 30 |
| Cucumbers | May 4 – May 11 | Jun 15 – Jun 22 | Jun 8 – Jun 22 | — |
| Zucchini & Summer Squash | May 4 – May 11 | — | Jun 8 – Jun 22 | Jul 12 – Jul 26 |
| Winter Squash & Pumpkins Warning: Your frost-free season is about 111 days, which is tight for winter squash & pumpkins (100+ days). Choose early varieties and use transplants or row covers. | May 4 – May 11 | — | Jun 8 – Jun 22 | — |
| Melons & Watermelon | May 4 – May 11 | Jun 15 – Jun 29 | — | — |
| Carrots | — | — | May 11 – Jun 8 | Jun 28 – Jul 12 |
| Beets | — | — | May 11 – Jun 8 | Jul 12 – Jul 26 |
| Potatoes | — | — | May 11 – Jun 1 | — |
| Swiss Chard | — | — | May 18 – Jun 15 | Jul 12 – Jul 26 |
| Cilantro | — | — | May 18 – Jun 8 | Jul 26 – Aug 16 |
| Green Beans | — | — | Jun 8 – Jun 29 | — |
| Sweet Corn | — | — | Jun 8 – Jun 22 | — |
| Sweet Potatoes Warning: Your frost-free season is about 111 days, which is tight for sweet potatoes (100+ days). Choose early varieties and use transplants or row covers. | — | Jun 15 – Jul 6 | — | — |
| Garlic | — | — | — | Sep 6 – Oct 11 |
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 Mackay Lost Rvr Rs, ID weather station, about 1 km away (elevation 5,896 ft (1,797 m)).
Frost dates near Mackay
- Moore May 22 · Sep 22
- Arco May 22 · Sep 22
- Howe May 24 · Sep 14
- Sun Valley frost any month
- Hailey May 13 · Oct 2
- Bellevue May 13 · Oct 2
- Carey Jun 16 · Sep 9
- Ketchum frost any month
- Clayton May 14 · Sep 25
- Picabo Jun 16 · Sep 9
Frequently asked questions
When is the last frost in Mackay, ID?
The median last spring frost in Mackay, ID is June 1. There is still about a 10% chance of frost after June 21, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Mackay, ID?
The median first fall frost is September 20, with about a 10% chance of frost before September 4.
How long is the growing season in Mackay, ID?
About 111 days between the median last spring frost and first fall frost.
What planting zone is Mackay, ID?
Mackay, ID is in USDA hardiness zone 5a.