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Frost dates and planting calendar for Olympia, Washington

Updated October 30, 2026. Based on USDA, NOAA and Colorado State University Extension data. Published by Humblebee.

USDA hardiness zone
8b[1]
Median last spring frost
Apr 29[2]
Median first fall frost
Oct 14[3]
Growing season, median
169 days[4]

Olympia, Washington is in USDA hardiness zone 8b at the city center[1]. NOAA records from 1991 to 2020 put the median last spring frost on April 29[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 11, half of years Apr 29, 1 in 10 years after May 15Last frostmedian Apr 29First fall frost: 9 in 10 years before Nov 1, half of years Oct 14, 1 in 10 years before Sep 28First frostmedian Oct 14Frost riskHardyHardy vegetables: plant Apr 1 to Apr 15Apr 1 to Apr 15Semi-hardySemi-hardy vegetables: plant Apr 15 to Apr 29Apr 15 to Apr 29TenderTender vegetables: plant around Apr 29around Apr 29Very tenderVery tender vegetables: plant from May 13from May 13
Shaded: the span between the dates frost passes in 9 of 10 years and 1 of 10 years[2][3]. Green: planting windows from the CSU rules applied to the median last frost (GardenFacts calculation)[6]. Exact dates are in the tables below.

These dates are odds from NOAA records for 1991 to 2020, not a forecast. In half of years the last spring frost comes after April 29, and in 1 of 10 years it comes after May 15[2]. In half of years the first fall frost comes before October 14, and in 1 of 10 years it comes before September 28[3]. The dates come from the Olympia Airport weather station[5]. Any single year can be earlier or later.

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after April 11 after April 29 after May 15
First fall frost (32°F)[3] before September 28 before October 14 before November 1
  • Hard freeze (28°F): median last spring date April 5, median first fall date November 1[7].
  • Frost-free growing season: at least 144 days in 9 of 10 years, 169 days in half of years and 195 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 100% of years and 28°F or colder in 100% of years[8].
  • Weather station: Olympia Airport (USW00024227), 4.7 miles from the city center, 188 feet, 30 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension groups vegetables by how well they handle cold, and its guide was written for Colorado[6]. GardenFacts used the median last frost of April 29 as the average last frost[6]. Hardy vegetables such as broccoli, lettuce, peas and spinach can go in as early as 2 to 4 weeks before that date, which is April 1 to April 15[6]. Semi-hardy vegetables such as beets, carrots and potatoes can go in as early as 2 weeks before it, from April 15[9]. Very tender vegetables such as tomatoes, peppers and eggplant typically wait 2 or more weeks after it, so the earliest start is May 13[10].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 29) is April 1 to April 15[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 29) is April 15, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 29[11]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 29), is May 13[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Apr 1 Jun 5 (from transplants)
Cabbage (hardy)[12] Apr 1 Jun 25 (from transplants)
Kohlrabi (hardy)[12] Apr 1 May 21
Lettuce (hardy)[12] Apr 1 May 31
Onions (hardy)[12] Apr 1 Jul 20
Peas (hardy)[12] Apr 1 Jun 5
Radishes (hardy)[12] Apr 1 May 1
Spinach (hardy)[12] Apr 1 May 11
Turnips (hardy)[12] Apr 1 May 21
Beets (semi-hardy)[12] Apr 15 Jun 14
Carrots (semi-hardy)[12] Apr 15 Jun 24
Cauliflower (semi-hardy)[12] Apr 15 not listed
Parsnips (semi-hardy)[12] Apr 15 Jun 24
Potatoes (semi-hardy)[12] Apr 15 Aug 18
Swiss chard (semi-hardy)[12] Apr 15 Jun 14
Snap beans (tender)[12] Apr 29 Jun 28
Sweet corn (tender)[12] Apr 29 Jun 28
Cucumbers (tender)[12] Apr 29 Jun 23
Summer squash (tender)[12] Apr 29 Jun 18
Cantaloupe (very tender)[12] May 13 Aug 6
Eggplant (very tender)[12] May 13 Jul 12 (from transplants)
Peppers (very tender)[12] May 13 Jul 22 (from transplants)
Tomatoes (very tender)[12] May 13 Jul 17 (from transplants)
Winter squash (very tender)[12] May 13 Aug 21
Watermelon (very tender)[12] May 13 Aug 6
Spacing, depth and soil temperature (CSU Extension)
Vegetable Min. soil temp Depth Spacing Days to harvest
Broccoli[13] 40°F 1/2 in 18 in 65
Cabbage[13] 40°F 1/2 in 18 in 85
Kohlrabi[13] 40°F 1/2 in 7-9 in 50
Lettuce[13] 35°F 1/4 in 7-9 in 60
Onions[13] 35°F 1/4 in (seed), 1-2 in (sets) 4-6 in 110
Peas[13] 40°F 1 in 4-6 in 65
Radishes[13] 40°F 1/2 in 2-3 in 30
Spinach[13] 40°F 1/2 in 4-6 in 40
Turnips[13] 40°F 1/2 in 4-6 in 50
Beets[13] 40°F 3/4-1 in 4-6 in 60
Carrots[13] 40°F 1/4 in 2-3 in 70
Cauliflower[13] 40°F 1/2 in 18 in –
Parsnips[13] 35°F 1/2 in 5-6 in 70
Potatoes[13] 45°F – – 125
Swiss chard[13] 40°F 1 in 7-9 in 60
Snap beans[13] 55°F 1-1 1/2 in 6 in 60
Sweet corn[13] 50°F 1-1 1/2 in 12 x 30 in or 9 x 36 in 60-90
Cucumbers[13] 60°F 1 in 6 in trellised, 24-36 in untrellised 55
Summer squash[13] 60°F 1-1 1/2 in 36-48 in 50
Cantaloupe[13] 60°F 1-1 1/2 in 36-48 in 85
Eggplant[13] 60°F 1/4 in 18-24 in 60
Peppers[13] 60°F 1/4 in 15-18 in 70
Tomatoes[13] 50°F 1/4 in 24 in trellised 65
Winter squash[13] 60°F 1-1 1/2 in 36-48 in 100
Watermelon[13] 60°F 1-1 1/2 in 36-48 in 85

Hardiness zone

Zone 8b means the coldest night of the winter averages 15°F to 20°F, using 1991 to 2020 data[1]. The zone is about winter lows, not summer heat or frost dates[14]. Olympia spans more than one zone. By land area, 53% of the city lies in ZIP code areas rated 8b and 47% in areas rated 8a[15].

Zone 8b: average annual extreme minimum temperature 15°F to 20°F (1991 to 2020)[1]. Modeled value at the city center: 16.8°F[1].

Share of the city's land area by ZIP code zone: zone 8b 53%, zone 8a 47%[15].

All towns in zone 8b and what zone 8b means

Zone by ZIP code
ZIP code Zone Coldest night range
98501[15] 8a 10 to 15°F
98502[15] 8b 15 to 20°F
98506[15] 8b 15 to 20°F
98512[15] 8a 10 to 15°F
98516[15] 8b 15 to 20°F
98503[15] 8b 15 to 20°F

Questions people ask

What growing zone is Olympia, Washington?
The center of Olympia is in USDA zone 8b[1]. By land area, 47% of the city lies in ZIP code areas rated 8a[15].
When is the last frost in Olympia?
In half of years the last spring frost comes after April 29[2]. In 1 of 10 years it comes after May 15[2].
When to plant tomatoes in Olympia?
CSU Extension says tomatoes typically go in 2 or more weeks after the average last spring frost[10]. Using the median last frost, the earliest start is May 13[10].
When is the first frost in Olympia?
In half of years the first fall frost comes before October 14[3]. In 1 of 10 years it comes before September 28[3].
How long is the growing season in Olympia?
The growing season is at least 169 days in half of years[4]. It is at least 144 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Olympia, Washington in zone 8b. Zone 8b means an average annual extreme minimum temperature of 15°F to 20°F over 1991 to 2020. The map's modeled value at the city center is 16.8°F. USDA zone map 2023 (PRISM, OSU)
  2. Last spring frost (32°F) at this station: in 9 of 10 years the last frost comes after April 11, in half of years after April 29, and in 1 of 10 years after May 15 (NOAA 1991 to 2020 normals). The median last frost date is April 29. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before September 28, in half of years before October 14, and in 9 of 10 years before November 1 (NOAA 1991 to 2020 normals). The median first frost date is October 14. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 144 days in 9 of 10 years, at least 169 days in half of years, and at least 195 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Olympia Airport weather station (USW00024227), 4.7 miles from the center of Olympia at 188 feet, using 30 years of records from 1991 to 2020. NOAA Climate Normals 1991-2020
  6. Colorado State University Extension's vegetable planting guide (written for Colorado) groups broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips as hardy vegetables, with this rule: as early as 2-4 weeks before the average last... CSU Extension GardenNotes #720
  7. Hard freeze (28°F) at this station: the median last spring date is April 5 and the median first fall date is November 1. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 100% of years from 1991 to 2020, and 28°F or colder in 100% of years. NOAA Climate Normals 1991-2020
  9. Colorado State University Extension's vegetable planting guide (written for Colorado) groups beets, carrots, cauliflower, parsnips, potatoes, Swiss chard as semi-hardy vegetables, with this rule: as early as 0-2 weeks before the average last spring frost.... CSU Extension GardenNotes #720
  10. Colorado State University Extension's vegetable planting guide (written for Colorado) groups cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon as very tender vegetables, with this rule: typically 2 or more weeks after the average last... CSU Extension GardenNotes #720
  11. Colorado State University Extension's vegetable planting guide (written for Colorado) groups snap beans, sweet corn, cucumbers, summer squash as tender vegetables, with this rule: from seed around the average last spring frost; cucumber and summer squash... CSU Extension GardenNotes #720
  12. GardenFacts calculation: earliest planting date plus CSU days to harvest (table on this page), from the station's median last frost. NOAA Climate Normals 1991-2020
  13. CSU Extension vegetable table: soil temperature, depth, spacing, days to harvest (table on this page). CSU Extension GardenNotes #720
  14. USDA hardiness zones are based on the average annual extreme minimum winter temperature (the coldest night of each winter, averaged over 1991 to 2020 for the 2023 map), not on summer heat or frost dates. Each zone spans 10°F and each half zone (a or b)... USDA Plant Hardiness Zone Map
  15. Olympia, Washington overlaps 6 ZIP code areas. By land area, 53% lies in ZIP code areas rated zone 8b, 47% lies in ZIP code areas rated zone 8a. USDA zone map 2023 (PRISM, OSU)

Frost dates are probabilities from 1991 to 2020 weather records at one NOAA station, not a forecast. Any year can be earlier or later. The hardiness zone describes the average coldest winter night, not frost dates or summer heat. Spots inside the city can differ (ZIP table). Planting rules come from Colorado State University Extension's guide, written for Colorado. A local extension office may give dates tuned to the area. Planting and harvest dates marked GardenFacts calculation are simple arithmetic from the facts above, not advice from the source.

Hardiness zone data: USDA Plant Hardiness Zone Map (2023), USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu, accessed October 30, 2026. This is not the official USDA map. Frost data: NOAA NCEI U.S. Climate Normals 1991-2020. Planting rules: Colorado State University Extension.