Petersburg, AK frost dates
Last spring frostApr 29median date
First fall frostOct 17median date
Growing season171 daysfrost-free
Hardiness zone7bZone 7b
How Petersburg compares
- In 8 years out of 10, the last spring frost in Petersburg falls between April 15 and May 14, a 29-day window. The first fall frost falls between September 30 and November 1.
- The median last frost is 22 days earlier than the Alaska median of May 21.
- Its 171-day growing season is longer than 90% of the 165 Alaska places with a regular frost season (state median 124 days).
- The last frost is 24 days later than the zone 7b median of Apr 5. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 7b chart.
- The weather station records an average of 115 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 15 |
| 50% (median) | April 29 |
| 10% (safe for tender plants) | May 14 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 30 |
| 50% (median) | October 17 |
| 90% (late) | November 1 |
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 Petersburg, AK
Petersburg, AK frost dates — last frost Apr 29, first frost Oct 17, zone 7b. whenisthelastfrost.com
Crop
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Start indoors: Feb 4 to Feb 18Transplant outside: Apr 1 to Apr 15
Start indoors: Feb 18 to Mar 4Transplant outside: May 13 to May 27
Start indoors: Feb 18 to Mar 4Transplant outside: May 13 to May 27
Start indoors: Mar 4 to Mar 18Transplant outside: May 6 to May 20
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 8 to Apr 22Sow outdoors: Apr 1 to May 6Plant for fall: Aug 22 to Sep 19
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 1 to Apr 15Sow outdoors: Apr 1 to Apr 15Plant for fall: Aug 8 to Aug 29
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 15 to Apr 29Plant for fall: Jul 11 to Aug 1
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 8 to Apr 22Plant for fall: Jul 11 to Aug 1
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 15 to Apr 29Plant for fall: Jul 11 to Aug 1
Start indoors: Mar 18 to Apr 1Transplant outside: May 20 to Jun 3Sow outdoors: May 20 to Jun 3
Start indoors: Mar 18 to Apr 1Transplant outside: May 6 to May 20
Sow outdoors: Mar 18 to Apr 8Plant for fall: Jul 25 to Aug 15
Sow outdoors: Mar 18 to Apr 8Plant for fall: Aug 22 to Sep 12
Sow outdoors: Mar 25 to May 6Plant for fall: Sep 5 to Sep 26
Start indoors: Apr 1 to Apr 8Transplant outside: May 13 to May 20Sow outdoors: May 6 to May 20Plant for fall: Aug 1 to Aug 15
Start indoors: Apr 1 to Apr 8Sow outdoors: May 6 to May 20Plant for fall: Aug 8 to Aug 22
Start indoors: Apr 1 to Apr 8Sow outdoors: May 6 to May 20
Start indoors: Apr 1 to Apr 8Transplant outside: May 13 to May 27
Sow outdoors: Apr 8 to May 6Plant for fall: Jul 25 to Aug 8
Sow outdoors: Apr 8 to May 6Plant for fall: Aug 8 to Aug 22
Sow outdoors: Apr 8 to Apr 29
Sow outdoors: Apr 15 to May 13Plant for fall: Aug 8 to Aug 22
Sow outdoors: Apr 15 to May 6Plant for fall: Aug 22 to Sep 12
Sow outdoors: May 6 to May 27Plant for fall: Aug 1 to Aug 15
Sow outdoors: May 6 to May 20
Transplant outside: May 13 to Jun 3
Plant for fall: Oct 3 to Nov 7
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Petersburg, AK
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 4 – Feb 18 | Apr 1 – Apr 15 | — | — |
| Peppers | Feb 18 – Mar 4 | May 13 – May 27 | — | — |
| Eggplant | Feb 18 – Mar 4 | May 13 – May 27 | — | — |
| Tomatoes | Mar 4 – Mar 18 | May 6 – May 20 | — | — |
| Lettuce | Mar 4 – Mar 18 | Apr 8 – Apr 22 | Apr 1 – May 6 | Aug 22 – Sep 19 |
| Kale | Mar 4 – Mar 18 | Apr 1 – Apr 15 | Apr 1 – Apr 15 | Aug 8 – Aug 29 |
| Broccoli | Mar 4 – Mar 18 | Apr 15 – Apr 29 | — | Jul 11 – Aug 1 |
| Cabbage | Mar 4 – Mar 18 | Apr 8 – Apr 22 | — | Jul 11 – Aug 1 |
| Cauliflower | Mar 4 – Mar 18 | Apr 15 – Apr 29 | — | Jul 11 – Aug 1 |
| Okra | Mar 18 – Apr 1 | May 20 – Jun 3 | May 20 – Jun 3 | — |
| Basil | Mar 18 – Apr 1 | May 6 – May 20 | — | — |
| Peas | — | — | Mar 18 – Apr 8 | Jul 25 – Aug 15 |
| Spinach | — | — | Mar 18 – Apr 8 | Aug 22 – Sep 12 |
| Radishes | — | — | Mar 25 – May 6 | Sep 5 – Sep 26 |
| Cucumbers | Apr 1 – Apr 8 | May 13 – May 20 | May 6 – May 20 | Aug 1 – Aug 15 |
| Zucchini & Summer Squash | Apr 1 – Apr 8 | — | May 6 – May 20 | Aug 8 – Aug 22 |
| Winter Squash & Pumpkins | Apr 1 – Apr 8 | — | May 6 – May 20 | — |
| Melons & Watermelon | Apr 1 – Apr 8 | May 13 – May 27 | — | — |
| Carrots | — | — | Apr 8 – May 6 | Jul 25 – Aug 8 |
| Beets | — | — | Apr 8 – May 6 | Aug 8 – Aug 22 |
| Potatoes | — | — | Apr 8 – Apr 29 | — |
| Swiss Chard | — | — | Apr 15 – May 13 | Aug 8 – Aug 22 |
| Cilantro | — | — | Apr 15 – May 6 | Aug 22 – Sep 12 |
| Green Beans | — | — | May 6 – May 27 | Aug 1 – Aug 15 |
| Sweet Corn | — | — | May 6 – May 20 | — |
| Sweet Potatoes | — | May 13 – Jun 3 | — | — |
| Garlic | — | — | — | Oct 3 – Nov 7 |
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 Petersburg, AK weather station, 14 km away (elevation 108 ft (33 m)).
Frost dates near Petersburg
- Kake Apr 29 · Oct 25
- Point Baker Apr 19 · Oct 25
- Wrangell Apr 11 · Nov 1
- Coffman Cove May 1 · Oct 13
- Port Alexander Apr 18 · Nov 5
- Angoon Apr 29 · Oct 25
- Meyers Chuck May 1 · Oct 13
- Sitka May 3 · Oct 18
- Thorne Bay May 1 · Oct 13
- Klawock Apr 29 · Oct 16
Frequently asked questions
When is the last frost in Petersburg, AK?
The median last spring frost in Petersburg, AK is April 29. There is still about a 10% chance of frost after May 14, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Petersburg, AK?
The median first fall frost is October 17, with about a 10% chance of frost before September 30.
How long is the growing season in Petersburg, AK?
About 171 days between the median last spring frost and first fall frost.
What planting zone is Petersburg, AK?
Petersburg, AK is in USDA hardiness zone 7b.