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Frost dates and planting calendar for Frederick, Maryland

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

USDA hardiness zone
7b[1]
Median last spring frost
Apr 22[2]
Median first fall frost
Oct 20[3]
Growing season, median
179 days[4]

The center of Frederick, Maryland is in USDA hardiness zone 7b[1]. The median last spring frost is April 22, which means that in half of years the last frost comes after that date[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 7, half of years Apr 22, 1 in 10 years after May 9Last frostmedian Apr 22First fall frost: 9 in 10 years before Nov 2, half of years Oct 20, 1 in 10 years before Oct 7First frostmedian Oct 20Frost riskHardyHardy vegetables: plant Mar 25 to Apr 8Mar 25 to Apr 8Semi-hardySemi-hardy vegetables: plant Apr 8 to Apr 22Apr 8 to Apr 22TenderTender vegetables: plant around Apr 22around Apr 22Very tenderVery tender vegetables: plant from May 6from May 6
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.

NOAA records from 1991 to 2020 give the odds for frost in Frederick[2]. In 9 of 10 years the last spring frost comes after April 7, and in 1 of 10 years it comes after May 9[2]. In the fall, the first frost comes before October 20 in half of years, and before November 2 in 9 of 10 years[3]. These dates are chances, not promises, so any year can be earlier or later[2]. They come from the Emmitsburg 2SE weather station near Frederick[5].

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after April 7 after April 22 after May 9
First fall frost (32°F)[3] before October 7 before October 20 before November 2
  • Hard freeze (28°F): median last spring date April 9, median first fall date October 31[7].
  • Frost-free growing season: at least 158 days in 9 of 10 years, 179 days in half of years and 200 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: Emmitsburg 2SE (USC00182906), 18.1 miles from the city center, 403 feet, 25 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension wrote its vegetable planting guide for Colorado, so treat these dates as a starting point for Frederick[6]. We use the median last frost of April 22 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 it, which is March 25 to April 8[6]. Semi-hardy vegetables such as carrots, potatoes and beets can go in as early as April 8[9]. Tender vegetables such as snap beans and sweet corn can be sown from seed around April 22[10]. Very tender vegetables such as tomatoes and peppers typically start 2 or more weeks after the median last frost, so the earliest start is May 6[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 22) is March 25 to April 8[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 22) is April 8, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 22[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 22), is May 6[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 25 May 29 (from transplants)
Cabbage (hardy)[12] Mar 25 Jun 18 (from transplants)
Kohlrabi (hardy)[12] Mar 25 May 14
Lettuce (hardy)[12] Mar 25 May 24
Onions (hardy)[12] Mar 25 Jul 13
Peas (hardy)[12] Mar 25 May 29
Radishes (hardy)[12] Mar 25 Apr 24
Spinach (hardy)[12] Mar 25 May 4
Turnips (hardy)[12] Mar 25 May 14
Beets (semi-hardy)[12] Apr 8 Jun 7
Carrots (semi-hardy)[12] Apr 8 Jun 17
Cauliflower (semi-hardy)[12] Apr 8 not listed
Parsnips (semi-hardy)[12] Apr 8 Jun 17
Potatoes (semi-hardy)[12] Apr 8 Aug 11
Swiss chard (semi-hardy)[12] Apr 8 Jun 7
Snap beans (tender)[12] Apr 22 Jun 21
Sweet corn (tender)[12] Apr 22 Jun 21
Cucumbers (tender)[12] Apr 22 Jun 16
Summer squash (tender)[12] Apr 22 Jun 11
Cantaloupe (very tender)[12] May 6 Jul 30
Eggplant (very tender)[12] May 6 Jul 5 (from transplants)
Peppers (very tender)[12] May 6 Jul 15 (from transplants)
Tomatoes (very tender)[12] May 6 Jul 10 (from transplants)
Winter squash (very tender)[12] May 6 Aug 14
Watermelon (very tender)[12] May 6 Jul 30
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 7b means the coldest night of a typical winter is 5°F to 10°F, averaged over 1991 to 2020[1]. The zone is about winter lows, not summer heat or frost dates[14]. Frederick spans two zones[15]. By land area, 91% lies in ZIP code areas rated zone 7a and 9% in areas rated zone 7b[15].

Zone 7b: average annual extreme minimum temperature 5°F to 10°F (1991 to 2020)[1]. Modeled value at the city center: 5.9°F[1].

Share of the city's land area by ZIP code zone: zone 7a 91%, zone 7b 9%[15].

All towns in zone 7b and what zone 7b means

Zone by ZIP code
ZIP code Zone Coldest night range
21701[15] 7a 0 to 5°F
21702[15] 7a 0 to 5°F
21703[15] 7b 5 to 10°F
21704[15] 7a 0 to 5°F
21705[15] 7b 5 to 10°F

Questions people ask

What growing zone is Frederick, Maryland?
The center of Frederick is in USDA zone 7b[1]. By land area, 91% of the city is in ZIP code areas rated zone 7a[15].
When is the last frost in Frederick?
The median last spring frost is April 22, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after May 9[2].
When to plant tomatoes in Frederick?
CSU Extension says tomatoes typically go in 2 or more weeks after the average last spring frost[11]. Using the median last frost of April 22, the earliest start is May 6[11].
When is the first frost in Frederick?
The median first fall frost is October 20, so in half of years the first frost comes before that date[3]. In 1 of 10 years it comes before October 7[3].
How long is the growing season in Frederick?
The growing season is at least 179 days in half of years[4]. It is at least 158 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Frederick, Maryland in zone 7b. Zone 7b means an average annual extreme minimum temperature of 5°F to 10°F over 1991 to 2020. The map's modeled value at the city center is 5.9°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 7, in half of years after April 22, and in 1 of 10 years after May 9 (NOAA 1991 to 2020 normals). The median last frost date is April 22. 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 7, in half of years before October 20, and in 9 of 10 years before November 2 (NOAA 1991 to 2020 normals). The median first frost date is October 20. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 158 days in 9 of 10 years, at least 179 days in half of years, and at least 200 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Emmitsburg 2SE weather station (USC00182906), 18.1 miles from the center of Frederick at 403 feet, using 25 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 9 and the median first fall date is October 31. 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 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. Frederick, Maryland overlaps 5 ZIP code areas. By land area, 91% lies in ZIP code areas rated zone 7a, 9% lies in ZIP code areas rated zone 7b. 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.