Frost dates for Gaithersburg, Maryland
In Gaithersburg, half of springs have had their last frost by April 1 (and 1 spring in 10 still has one after April 15), and half of falls have had their first frost by November 6, leaving about 219 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Gaithersburg, Maryland
Last spring frost
April 1
Half of springs have their last frost by this date. For a safer bet, wait until April 15: only 1 spring in 10 has a frost after that.
First fall frost
November 6
Half of falls have their first frost by this date. In 1 fall in 10 it comes by October 24.
Growing season
219 days
Frost-free days in a typical year. 9 years in 10 get at least 200.
Hardiness zone
7b
2023 USDA map: the coldest night of winter averages 5°F to 10°F. On the 2012 map it was 7a, half a zone colder. All 11 ZIP codes within about 6 miles of the city's center are in zone 7b.
Print a year planner for Gaithersburg
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | March 19 | April 1 | April 15 |
| First frost in fall | October 24 | November 6 | November 21 |
The frost-free season between them runs 219 days in a typical year. In 1 year in 10 it is 240 days or longer, and in 1 year in 10 it is 200 days or shorter.
- Hard freeze (28°F): typically last on March 22 and first on November 19. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on April 16 and first on October 25. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
In 8 springs out of 10, the last frost in Gaithersburg comes between March 19 and April 15, a window of 27 days. That is narrower than at most NOAA stations (the typical window is 31 days), so the typical date is a steadier guide here than in most places.
Among Maryland's 43 NOAA stations with a frost every year, 74 percent have their typical last frost later than Gaithersburg does.
Planting calendar for Gaithersburg
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
| When | What to do | Why then |
|---|---|---|
| January | ||
| January 14 to February 11 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| January 28 to February 25 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| February | ||
| February 11 to March 4 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| February 18 to March 4 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| February 25 to March 11 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| March | ||
| March 4 to 18 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| March 4 to 18 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| March 18 to April 1 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| March 18 to April 1 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| April | ||
| April 1 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| April 15 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| April 15 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| June | ||
| June 11 to 25 | Cabbage for fall Start seeds | set the plants out by July 30 |
| July | ||
| July 1 to 15 | Broccoli for fall Start seeds | set the plants out by August 19 |
| August | ||
| August 10 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 14 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| August 15 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 19 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| August 20 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 24 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| September | ||
| September 3 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| September 13 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| September 23 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| October | ||
| October 24 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| November | ||
| November 26 to December 3 | Garlic Plant cloves | one or two weeks after the typical first hard freeze (28°F), our reading of the first killing frost |
Want more insurance? Shift every spring date 14 days later. That plans around April 15, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Rockville 1 NE (station USC00187705), 4 miles from the center of Gaithersburg. It sits at about the same elevation, 440 feet above sea level. NOAA rates this station's record as representative: at least 10 of the 30 years, with the gaps filled from nearby stations.
The same station also gives the frost dates for Rockville.
Our ZIP code lookup matches these 26 ZIP codes to the same station, so they get the same dates: 20832, 20833, 20841, 20850, 20851, 20852, 20853, 20854, 20855, 20860, 20862, 20874, 20877, 20878, 20879, 20880, 20886, 20892, 20894, 20895, 20896, 20899, 20902, 20906, 21036, 21737. Hardiness zones are worked out separately for each ZIP code.
Nearby places
- Washington, District of Columbia: last frost around March 24, first frost around November 18 (20 miles away)
- Frederick, Maryland: last frost around April 2, first frost around November 6 (25 miles away)
- Baltimore, Maryland: last frost around March 24, first frost around November 21 (35 miles away)
See frost dates across Maryland, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.