Frost Dates for Lake Oswego, OR 97035

Last spring frost March 23 · First fall frost November 15 · 237 frost-free days · USDA Zone 9a

Frost probability for 97035

Frost10%50%90%
Spring (last frost)April 22March 23February 27
Fall (first frost)October 21November 15December 6

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (11.4 km away); the 50% date is the median year.

Frost dates by ZIP code in Lake Oswego, OR

ZIPLast spring frost (50%)First fall frost (50%)Zone
97035March 23November 159a
97034March 23November 159a

Month by month in Lake Oswego

MonthWhat to do
JanuaryStart peppers and eggplant indoors 8–10 weeks before your last frost (around March 23). Start tomatoes about two weeks later, 6–8 weeks before last frost.
FebruaryStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
MarchLast frost around March 23. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
AprilFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
MaySuccession plant lettuce and greens. Keep beds weeded and watered consistently.
JuneHarvest regularly to encourage production. Monitor for pests and disease.
JulyMidsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall.
AugustDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
SeptemberDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
OctoberFirst fall frost approaching (around November 15). Transplant fall brassicas. Sow spinach, arugula, and radishes.
NovemberFirst frost around November 15. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.
DecemberHarvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year.

What grows in a 237-day season

Frequently Asked Questions

What is the last frost date for Lake Oswego, OR (ZIP 97035)?

The median last spring frost date for Lake Oswego, OR (ZIP code 97035) is around March 23. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.

What is the first fall frost date in Lake Oswego, OR?

The median first fall frost date for Lake Oswego, OR is around November 15. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.

How long is the growing season in Lake Oswego, OR?

The frost-free growing season in Lake Oswego is about 237 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.

What USDA hardiness zone is Lake Oswego, OR?

Based on frost date patterns, Lake Oswego falls approximately in 9a. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.

When should I start tomatoes indoors in Lake Oswego, OR?

Start tomato seeds indoors 6–8 weeks before your last frost date (around March 23). For Lake Oswego, that's roughly January 27 to February 10. Transplant outdoors 1–2 weeks after your last frost.

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