Frost dates for 97034 — Lake Oswego, OR
Last spring frostMar 18median date
First fall frostNov 18median date
Growing season245 daysfrost-free
Hardiness zone9aZone 9a
How Lake Oswego compares
- In 8 years out of 10, the last spring frost in Lake Oswego falls between February 19 and April 11, a 51-day window. The first fall frost falls between October 30 and December 12.
- The median last frost is 29 days earlier than the Oregon median of Apr 16.
- Its 245-day growing season is longer than 85% of the 345 Oregon places with a regular frost season (state median 193 days).
- The last frost is 15 days later than the zone 9a median of Mar 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 9a chart.
- The weather station records an average of 30 nights a year at or below 32°F.
- Compared with Portland, OR, 12 km away, the last frost here is 21 days later than there and the growing season is 34 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | February 19 |
| 50% (median) | March 18 |
| 10% (safe for tender plants) | April 11 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 30 |
| 50% (median) | November 18 |
| 90% (late) | December 12 |
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 Lake Oswego, OR
Frost dates for 97034 — Lake Oswego, OR — last frost Mar 18, first frost Nov 18, zone 9a. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Dec 24 to Jan 7Start indoors: Dec 24 to Jan 7Transplant outside: Feb 18 to Mar 4
Start indoors: Jan 7 to Jan 21Transplant outside: Apr 1 to Apr 15
Start indoors: Jan 7 to Jan 21Transplant outside: Apr 1 to Apr 15
Start indoors: Jan 21 to Feb 4Transplant outside: Mar 25 to Apr 8
Start indoors: Jan 21 to Feb 4Transplant outside: Feb 25 to Mar 11Sow outdoors: Feb 18 to Mar 25Plant for fall: Sep 23 to Oct 21
Start indoors: Jan 21 to Feb 4Transplant outside: Feb 18 to Mar 4Sow outdoors: Feb 18 to Mar 4Plant for fall: Sep 9 to Sep 30
Start indoors: Jan 21 to Feb 4Transplant outside: Mar 4 to Mar 18Plant for fall: Aug 12 to Sep 2
Start indoors: Jan 21 to Feb 4Transplant outside: Feb 25 to Mar 11Plant for fall: Aug 12 to Sep 2
Start indoors: Jan 21 to Feb 4Transplant outside: Mar 4 to Mar 18Plant for fall: Aug 12 to Sep 2
Start indoors: Feb 4 to Feb 18Transplant outside: Apr 8 to Apr 22Sow outdoors: Apr 8 to Apr 22
Start indoors: Feb 4 to Feb 18Transplant outside: Mar 25 to Apr 8
Sow outdoors: Feb 4 to Feb 25Plant for fall: Aug 26 to Sep 16
Sow outdoors: Feb 4 to Feb 25Plant for fall: Sep 23 to Oct 14
Sow outdoors: Feb 11 to Mar 25Plant for fall: Oct 7 to Oct 28
Start indoors: Feb 18 to Feb 25Transplant outside: Apr 1 to Apr 8Sow outdoors: Mar 25 to Apr 8Plant for fall: Sep 2 to Sep 16
Start indoors: Feb 18 to Feb 25Sow outdoors: Mar 25 to Apr 8Plant for fall: Sep 9 to Sep 23
Start indoors: Feb 18 to Feb 25Sow outdoors: Mar 25 to Apr 8
Start indoors: Feb 18 to Feb 25Transplant outside: Apr 1 to Apr 15
Sow outdoors: Feb 25 to Mar 25Plant for fall: Aug 26 to Sep 9
Sow outdoors: Feb 25 to Mar 25Plant for fall: Sep 9 to Sep 23
Sow outdoors: Feb 25 to Mar 18
Sow outdoors: Mar 4 to Apr 1Plant for fall: Sep 9 to Sep 23
Sow outdoors: Mar 4 to Mar 25Plant for fall: Sep 23 to Oct 14
Sow outdoors: Mar 25 to Apr 15Plant for fall: Sep 2 to Sep 16
Sow outdoors: Mar 25 to Apr 8
Transplant outside: Apr 1 to Apr 22
Plant for fall: Nov 4 to Dec 9
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Lake Oswego, OR
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Dec 24 – Jan 7 | Feb 18 – Mar 4 | — | — |
| Peppers | Jan 7 – Jan 21 | Apr 1 – Apr 15 | — | — |
| Eggplant | Jan 7 – Jan 21 | Apr 1 – Apr 15 | — | — |
| Tomatoes | Jan 21 – Feb 4 | Mar 25 – Apr 8 | — | — |
| Lettuce | Jan 21 – Feb 4 | Feb 25 – Mar 11 | Feb 18 – Mar 25 | Sep 23 – Oct 21 |
| Kale | Jan 21 – Feb 4 | Feb 18 – Mar 4 | Feb 18 – Mar 4 | Sep 9 – Sep 30 |
| Broccoli | Jan 21 – Feb 4 | Mar 4 – Mar 18 | — | Aug 12 – Sep 2 |
| Cabbage | Jan 21 – Feb 4 | Feb 25 – Mar 11 | — | Aug 12 – Sep 2 |
| Cauliflower | Jan 21 – Feb 4 | Mar 4 – Mar 18 | — | Aug 12 – Sep 2 |
| Okra | Feb 4 – Feb 18 | Apr 8 – Apr 22 | Apr 8 – Apr 22 | — |
| Basil | Feb 4 – Feb 18 | Mar 25 – Apr 8 | — | — |
| Peas | — | — | Feb 4 – Feb 25 | Aug 26 – Sep 16 |
| Spinach | — | — | Feb 4 – Feb 25 | Sep 23 – Oct 14 |
| Radishes | — | — | Feb 11 – Mar 25 | Oct 7 – Oct 28 |
| Cucumbers | Feb 18 – Feb 25 | Apr 1 – Apr 8 | Mar 25 – Apr 8 | Sep 2 – Sep 16 |
| Zucchini & Summer Squash | Feb 18 – Feb 25 | — | Mar 25 – Apr 8 | Sep 9 – Sep 23 |
| Winter Squash & Pumpkins | Feb 18 – Feb 25 | — | Mar 25 – Apr 8 | — |
| Melons & Watermelon | Feb 18 – Feb 25 | Apr 1 – Apr 15 | — | — |
| Carrots | — | — | Feb 25 – Mar 25 | Aug 26 – Sep 9 |
| Beets | — | — | Feb 25 – Mar 25 | Sep 9 – Sep 23 |
| Potatoes | — | — | Feb 25 – Mar 18 | — |
| Swiss Chard | — | — | Mar 4 – Apr 1 | Sep 9 – Sep 23 |
| Cilantro | — | — | Mar 4 – Mar 25 | Sep 23 – Oct 14 |
| Green Beans | — | — | Mar 25 – Apr 15 | Sep 2 – Sep 16 |
| Sweet Corn | — | — | Mar 25 – Apr 8 | — |
| Sweet Potatoes | — | Apr 1 – Apr 22 | — | — |
| Garlic | — | — | — | Nov 4 – Dec 9 |
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 Oregon City, OR weather station, 9 km away (elevation 167 ft (51 m)).
ZIP codes in Lake Oswego: 97034 97035
Frost dates near Lake Oswego
- Marylhurst Mar 18 · Nov 18
- West Linn Mar 18 · Nov 18
- Tualatin Apr 1 · Nov 6
- Gladstone Mar 18 · Nov 18
- Oregon City Mar 18 · Nov 18
- Happy Valley Mar 18 · Nov 18
- Portland Feb 25 · Dec 1
- Clackamas Mar 18 · Nov 18
Frequently asked questions
When is the last frost in Lake Oswego, OR?
The median last spring frost in Lake Oswego, OR is March 18. There is still about a 10% chance of frost after April 11, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Lake Oswego, OR?
The median first fall frost is November 18, with about a 10% chance of frost before October 30.
How long is the growing season in Lake Oswego, OR?
About 245 days between the median last spring frost and first fall frost.
What planting zone is Lake Oswego, OR?
Lake Oswego, OR is in USDA hardiness zone 9a.