Porthill, ID frost dates
Last spring frostMay 4median date
First fall frostSep 30median date
Growing season149 daysfrost-free
Hardiness zone—
How Porthill compares
- In 8 years out of 10, the last spring frost in Porthill falls between April 20 and May 28, a 38-day window. The first fall frost falls between September 10 and October 14.
- The median last frost is 10 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 weather station records an average of 162 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 20 |
| 50% (median) | May 4 |
| 10% (safe for tender plants) | May 28 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 10 |
| 50% (median) | September 30 |
| 90% (late) | October 14 |
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 Porthill, ID
Porthill, ID frost dates — last frost May 4, first frost Sep 30, zone n/a. whenisthelastfrost.com
Crop
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Start indoors: Feb 9 to Feb 23Transplant outside: Apr 6 to Apr 20
Start indoors: Feb 23 to Mar 9Transplant outside: May 18 to Jun 1
Start indoors: Feb 23 to Mar 9Transplant outside: May 18 to Jun 1
Start indoors: Mar 9 to Mar 23Transplant outside: May 11 to May 25
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 13 to Apr 27Sow outdoors: Apr 6 to May 11Plant for fall: Aug 5 to Sep 2
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 6 to Apr 20Sow outdoors: Apr 6 to Apr 20Plant for fall: Jul 22 to Aug 12
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 20 to May 4Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 13 to Apr 27Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 20 to May 4Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 23 to Apr 6Transplant outside: May 25 to Jun 8Sow outdoors: May 25 to Jun 8
Start indoors: Mar 23 to Apr 6Transplant outside: May 11 to May 25
Sow outdoors: Mar 23 to Apr 13Plant for fall: Jul 8 to Jul 29
Sow outdoors: Mar 23 to Apr 13Plant for fall: Aug 5 to Aug 26
Sow outdoors: Mar 30 to May 11Plant for fall: Aug 19 to Sep 9
Start indoors: Apr 6 to Apr 13Transplant outside: May 18 to May 25Sow outdoors: May 11 to May 25Plant for fall: Jul 15 to Jul 29
Start indoors: Apr 6 to Apr 13Sow outdoors: May 11 to May 25Plant for fall: Jul 22 to Aug 5
Start indoors: Apr 6 to Apr 13Sow outdoors: May 11 to May 25
Start indoors: Apr 6 to Apr 13Transplant outside: May 18 to Jun 1
Sow outdoors: Apr 13 to May 11Plant for fall: Jul 8 to Jul 22
Sow outdoors: Apr 13 to May 11Plant for fall: Jul 22 to Aug 5
Sow outdoors: Apr 13 to May 4
Sow outdoors: Apr 20 to May 18Plant for fall: Jul 22 to Aug 5
Sow outdoors: Apr 20 to May 11Plant for fall: Aug 5 to Aug 26
Sow outdoors: May 11 to Jun 1Plant for fall: Jul 15 to Jul 29
Sow outdoors: May 11 to May 25
Transplant outside: May 18 to Jun 8
Plant for fall: Sep 16 to Oct 21
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Porthill, ID
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 9 – Feb 23 | Apr 6 – Apr 20 | — | — |
| Peppers | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Eggplant | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Tomatoes | Mar 9 – Mar 23 | May 11 – May 25 | — | — |
| Lettuce | Mar 9 – Mar 23 | Apr 13 – Apr 27 | Apr 6 – May 11 | Aug 5 – Sep 2 |
| Kale | Mar 9 – Mar 23 | Apr 6 – Apr 20 | Apr 6 – Apr 20 | Jul 22 – Aug 12 |
| Broccoli | Mar 9 – Mar 23 | Apr 20 – May 4 | — | Jun 24 – Jul 15 |
| Cabbage | Mar 9 – Mar 23 | Apr 13 – Apr 27 | — | Jun 24 – Jul 15 |
| Cauliflower | Mar 9 – Mar 23 | Apr 20 – May 4 | — | Jun 24 – Jul 15 |
| Okra | Mar 23 – Apr 6 | May 25 – Jun 8 | May 25 – Jun 8 | — |
| Basil | Mar 23 – Apr 6 | May 11 – May 25 | — | — |
| Peas | — | — | Mar 23 – Apr 13 | Jul 8 – Jul 29 |
| Spinach | — | — | Mar 23 – Apr 13 | Aug 5 – Aug 26 |
| Radishes | — | — | Mar 30 – May 11 | Aug 19 – Sep 9 |
| Cucumbers | Apr 6 – Apr 13 | May 18 – May 25 | May 11 – May 25 | Jul 15 – Jul 29 |
| Zucchini & Summer Squash | Apr 6 – Apr 13 | — | May 11 – May 25 | Jul 22 – Aug 5 |
| Winter Squash & Pumpkins | Apr 6 – Apr 13 | — | May 11 – May 25 | — |
| Melons & Watermelon | Apr 6 – Apr 13 | May 18 – Jun 1 | — | — |
| Carrots | — | — | Apr 13 – May 11 | Jul 8 – Jul 22 |
| Beets | — | — | Apr 13 – May 11 | Jul 22 – Aug 5 |
| Potatoes | — | — | Apr 13 – May 4 | — |
| Swiss Chard | — | — | Apr 20 – May 18 | Jul 22 – Aug 5 |
| Cilantro | — | — | Apr 20 – May 11 | Aug 5 – Aug 26 |
| Green Beans | — | — | May 11 – Jun 1 | Jul 15 – Jul 29 |
| Sweet Corn | — | — | May 11 – May 25 | — |
| Sweet Potatoes | — | May 18 – Jun 8 | — | — |
| Garlic | — | — | — | Sep 16 – Oct 21 |
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 Porthill 1 Sw, ID weather station, 2 km away (elevation 1,798 ft (548 m)).
Frost dates near Porthill
- Eastport May 4 · Sep 30
- Bonners Ferry Apr 30 · Oct 4
- Moyie Springs Apr 30 · Oct 4
- Naples Apr 30 · Oct 4
- Nordman May 20 · Sep 13
- Coolin May 20 · Sep 13
- Colburn May 8 · Sep 28
- Sandpoint May 8 · Sep 28
- Kootenai May 8 · Sep 28
- Ponderay May 8 · Sep 28
Frequently asked questions
When is the last frost in Porthill, ID?
The median last spring frost in Porthill, ID is May 4. There is still about a 10% chance of frost after May 28, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Porthill, ID?
The median first fall frost is September 30, with about a 10% chance of frost before September 10.
How long is the growing season in Porthill, ID?
About 149 days between the median last spring frost and first fall frost.
What planting zone is Porthill, ID?
Zone data is not available for this location.