Frost Dates for Klamath Falls, OR 97603

Last spring frost June 11 · First fall frost September 18 · 99 frost-free days · USDA Zone 6b

Frost probability for 97603

Frost10%50%90%
Spring (last frost)June 29June 11May 24
Fall (first frost)August 25September 18October 6

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (7.0 km away); the 50% date is the median year.

Frost dates by ZIP code in Klamath Falls, OR

ZIPLast spring frost (50%)First fall frost (50%)Zone
97603June 11September 186b
97601June 11September 187a

Month by month in Klamath Falls

MonthWhat to do
JanuaryPlan your garden layout and order seeds. Research varieties suited to your frost dates.
FebruaryStart the slowest-growing crops indoors: onions, leeks, and celery (10–12 weeks before last frost).
MarchOrganize planting supplies and seed-starting mix. Check stored garden tools.
AprilStart peppers and eggplant indoors 8–10 weeks before your last frost (around June 11). Start tomatoes about two weeks later, 6–8 weeks before last frost.
MayStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
JuneLast frost around June 11. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
JulyFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
AugustFirst fall frost approaching (around September 18). Transplant fall brassicas. Sow spinach, arugula, and radishes.
SeptemberFirst frost around September 18. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.
OctoberHarvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year.
NovemberClean up spent plants. Add compost to beds. Rest, review, and plan next year's garden.
DecemberClean up spent plants. Add compost to beds. Rest, review, and plan next year's garden.

What grows in a 99-day season

Frequently Asked Questions

What is the last frost date for Klamath Falls, OR (ZIP 97603)?

The median last spring frost date for Klamath Falls, OR (ZIP code 97603) is around June 11. 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 Klamath Falls, OR?

The median first fall frost date for Klamath Falls, OR is around September 18. 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 Klamath Falls, OR?

The frost-free growing season in Klamath Falls is about 99 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 Klamath Falls, OR?

Based on frost date patterns, Klamath Falls falls approximately in 6b. 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 Klamath Falls, OR?

Start tomato seeds indoors 6–8 weeks before your last frost date (around June 11). For Klamath Falls, that's roughly April 16 to April 30. Transplant outdoors 1–2 weeks after your last frost.

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