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Frost dates and planting calendar for Beaverton, Oregon

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

USDA hardiness zone
9a[1]
Median last spring frost
Apr 1[2]
Median first fall frost
Nov 6[3]
Growing season, median
222 days[4]

Beaverton, Oregon sits in USDA hardiness zone 9a[1]. The median last spring frost at the nearest NOAA station is April 1[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Mar 5, half of years Apr 1, 1 in 10 years after Apr 26Last frostmedian Apr 1First fall frost: 9 in 10 years before Dec 1, half of years Nov 6, 1 in 10 years before Oct 19First frostmedian Nov 6Frost riskHardyHardy vegetables: plant Mar 4 to Mar 18Mar 4 to Mar 18Semi-hardySemi-hardy vegetables: plant Mar 18 to Apr 1Mar 18 to Apr 1TenderTender vegetables: plant around Apr 1around Apr 1Very tenderVery tender vegetables: plant from Apr 15from Apr 15
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 frost dates are odds from NOAA records for 1991 to 2020, not a forecast. They come from the Beaverton 2SSW weather station[5]. The last spring frost comes after April 1 in half of years, and after April 26 in 1 of 10 years[2]. The first fall frost comes before November 6 in half of years, and before October 19 in 1 of 10 years[3]. 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 March 5 after April 1 after April 26
First fall frost (32°F)[3] before October 19 before November 6 before December 1
  • Hard freeze (28°F): median last spring date February 26, median first fall date November 30[7].
  • Frost-free growing season: at least 186 days in 9 of 10 years, 222 days in half of years and 254 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 100% of years and 28°F or colder in 99.7% of years[8].
  • Weather station: Beaverton 2SSW (USC00350595), 1.6 miles from the city center, 270 feet, 15 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension groups vegetables by how well they handle cold. Its guide was written for Colorado[6]. GardenFacts took the NOAA median last frost of April 1 as the average last frost[6]. Hardy vegetables such as broccoli, lettuce and peas can go in as early as 2 to 4 weeks before it, which is March 4 to March 18[6]. Semi-hardy vegetables such as carrots and potatoes can go in as early as 2 weeks before it, from March 18[9]. Tender vegetables such as snap beans and sweet corn can be started from seed around April 1[10]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after it, so the earliest start is April 15[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 1) is March 4 to March 18[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 1) is March 18, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 1[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 1), is April 15[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 4 May 8 (from transplants)
Cabbage (hardy)[12] Mar 4 May 28 (from transplants)
Kohlrabi (hardy)[12] Mar 4 Apr 23
Lettuce (hardy)[12] Mar 4 May 3
Onions (hardy)[12] Mar 4 Jun 22
Peas (hardy)[12] Mar 4 May 8
Radishes (hardy)[12] Mar 4 Apr 3
Spinach (hardy)[12] Mar 4 Apr 13
Turnips (hardy)[12] Mar 4 Apr 23
Beets (semi-hardy)[12] Mar 18 May 17
Carrots (semi-hardy)[12] Mar 18 May 27
Cauliflower (semi-hardy)[12] Mar 18 not listed
Parsnips (semi-hardy)[12] Mar 18 May 27
Potatoes (semi-hardy)[12] Mar 18 Jul 21
Swiss chard (semi-hardy)[12] Mar 18 May 17
Snap beans (tender)[12] Apr 1 May 31
Sweet corn (tender)[12] Apr 1 May 31
Cucumbers (tender)[12] Apr 1 May 26
Summer squash (tender)[12] Apr 1 May 21
Cantaloupe (very tender)[12] Apr 15 Jul 9
Eggplant (very tender)[12] Apr 15 Jun 14 (from transplants)
Peppers (very tender)[12] Apr 15 Jun 24 (from transplants)
Tomatoes (very tender)[12] Apr 15 Jun 19 (from transplants)
Winter squash (very tender)[12] Apr 15 Jul 24
Watermelon (very tender)[12] Apr 15 Jul 9
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 9a means the coldest night of the year averages 20°F to 25°F, based on 1991 to 2020[1]. The zone is not about summer heat or frost dates[14]. Beaverton is not all one zone. By land area, 52% of the city lies in ZIP code areas rated 9a and 48% in areas rated 8b[15].

Zone 9a: average annual extreme minimum temperature 20°F to 25°F (1991 to 2020)[1]. Modeled value at the city center: 20.5°F[1].

Share of the city's land area by ZIP code zone: zone 9a 52%, zone 8b 48%[15].

All towns in zone 9a and what zone 9a means

Zone by ZIP code
ZIP code Zone Coldest night range
97008[15] 9a 20 to 25°F
97007[15] 8b 15 to 20°F
97005[15] 9a 20 to 25°F
97006[15] 8b 15 to 20°F
97225[15] 8b 15 to 20°F
97003[15] 9a 20 to 25°F
97229[15] 8b 15 to 20°F
97223[15] 9a 20 to 25°F

Questions people ask

What growing zone is Beaverton, Oregon?
The 2023 USDA map puts the center of Beaverton in zone 9a[1]. About 48% of the city by land area is in ZIP code areas rated 8b[15].
When is the last frost in Beaverton?
The median last spring frost is April 1, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after April 26[2].
When to plant tomatoes in Beaverton?
CSU Extension lists tomatoes as very tender and typically 2 or more weeks after the average last frost[11]. Using the median last frost, the earliest start is April 15[11].
When is the first frost in Beaverton?
The median first fall frost is November 6[3]. In 1 of 10 years it comes before October 19[3].
How long is the growing season in Beaverton?
The growing season is at least 222 days in half of years[4]. It is at least 186 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Beaverton, Oregon in zone 9a. Zone 9a means an average annual extreme minimum temperature of 20°F to 25°F over 1991 to 2020. The map's modeled value at the city center is 20.5°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 March 5, in half of years after April 1, and in 1 of 10 years after April 26 (NOAA 1991 to 2020 normals). The median last frost date is April 1. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before October 19, in half of years before November 6, and in 9 of 10 years before December 1 (NOAA 1991 to 2020 normals). The median first frost date is November 6. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 186 days in 9 of 10 years, at least 222 days in half of years, and at least 254 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Beaverton 2SSW weather station (USC00350595), 1.6 miles from the center of Beaverton at 270 feet, using 15 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 February 26 and the median first fall date is November 30. 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 99.7% 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 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
  11. 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
  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. Beaverton, Oregon overlaps 8 ZIP code areas. By land area, 52% lies in ZIP code areas rated zone 9a, 48% lies in ZIP code areas rated zone 8b. 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.