USDA Hardiness Zone 7b
Frost Dates for 21043 — Ellicott City, Maryland
NOAA 1991–2020 normals from Baltimore Wash International Airport, MD (156 ft), 9 miles southeast.
Updated
In Ellicott City, the last spring frost (32°F) is around April 10 in half of years and has passed by April 25 in nine years out of ten. The first fall frost comes around October 31, as early as October 17 one year in ten, leaving a typical freeze-free season of 204 days (NOAA, Baltimore Wash International Airport, MD).
- Last spring frost
- April 10
- First fall frost
- October 31
- Growing season
- 204 days
- Hardiness zone
- 7b
50% probability
50% probability
freeze-free, 50%
5 to 10°F (-15.0 to -12.2°C) coldest night
- First snow
- December 11
- Last snow
- March 11
- Winters with snow
- 100%
- Snow per year
- 19.3"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Ellicott City
Half of springs at Baltimore Wash International Airport, MD see their last 32°F night by April 10; only one in ten is past it by March 27, and one in ten still has one after April 25. Planting tender crops after April 16 leaves a 30% risk of a frost on them, after April 19 20%, and after April 25 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 52% of the 50 Maryland stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 31 in half of years, as early as October 17 one year in ten, and holds off past November 12 one year in ten. A hard freeze of 28°F follows 10 days later, around November 10; in spring the one-in-ten date for 28°F is April 10, 15 days before the 32°F one. The freeze-free season lasts 204 days in a typical year, longer than at 54% of the 50 Maryland stations; it reaches 223 days one year in ten and falls short of 183 one year in ten. On average 93 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 14 days longer, to about April 24, and return around October 21. Severe cold of 16°F or below comes in 99% of winters, usually between December 27 and February 20.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 9 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 28 | May 1 | May 6 | May 12 |
| 32°F | Mar 27 | Mar 31 | Apr 3 | Apr 7 | Apr 10 | Apr 13 | Apr 16 | Apr 19 | Apr 25 |
| 28°F | Mar 13 | Mar 18 | Mar 21 | Mar 24 | Mar 28 | Mar 31 | Apr 2 | Apr 5 | Apr 10 |
| 24°F | Feb 28 | Mar 4 | Mar 9 | Mar 12 | Mar 16 | Mar 19 | Mar 22 | Mar 26 | Mar 31 |
| 20°F | Feb 13 | Feb 21 | Feb 25 | Mar 1 | Mar 4 | Mar 7 | Mar 11 | Mar 15 | Mar 20 |
| 16°F99% of yrs | Jan 28 | Feb 3 | Feb 9 | Feb 15 | Feb 20 | Feb 25 | Feb 28 | Mar 4 | Mar 10 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 8 | Oct 12 | Oct 15 | Oct 18 | Oct 21 | Oct 24 | Oct 26 | Oct 29 | Nov 2 |
| 32°F | Oct 17 | Oct 22 | Oct 26 | Oct 29 | Oct 31 | Nov 2 | Nov 5 | Nov 7 | Nov 12 |
| 28°F | Oct 30 | Nov 2 | Nov 5 | Nov 8 | Nov 10 | Nov 13 | Nov 17 | Nov 21 | Nov 27 |
| 24°F | Nov 8 | Nov 13 | Nov 17 | Nov 21 | Nov 25 | Nov 30 | Dec 2 | Dec 6 | Dec 13 |
| 20°F | Nov 20 | Nov 29 | Dec 2 | Dec 6 | Dec 10 | Dec 14 | Dec 19 | Dec 26 | Jan 1 |
| 16°F99% of yrs | Dec 5 | Dec 11 | Dec 17 | Dec 23 | Dec 27 | Jan 1 | Jan 4 | Jan 11 | Jan 21 |
Freeze probabilities 1991–2020 at Baltimore Wash International Airport, MD, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 21043 →Compare Ellicott City with another place →
Weather by month in Ellicott City
July is the warmest month at Baltimore Wash International Airport, MD, averaging 89°F by day and 68°F at night; January is the coldest at 43°F and 25°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 78% of years.
Warmth for growing adds up to 4,007 growing degree days a year (base 50°F), more than at 62% of the 50 Maryland stations. 35% of them (1,415) have built up by the end of June, and July adds the most, 876. Precipitation totals 45.0 inches a year, most in July (4.5") and least in February (2.9"); May to September bring 46% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 43 | 25 | 3.1 | 100% | 24 | 7 |
| Feb | 46 | 27 | 2.9 | 100% | 21 | 10 |
| Mar | 55 | 34 | 4.0 | 100% | 14 | 52 |
| Apr | 67 | 44 | 3.4 | 78% | 2 | 194 |
| May | 76 | 53 | 3.9 | 6% | 0 | 447 |
| Jun | 84 | 63 | 4.0 | 0% | 0 | 705 |
| Jul | 89 | 68 | 4.5 | 0% | 0 | 876 |
| Aug | 87 | 66 | 4.1 | 0% | 0 | 811 |
| Sep | 80 | 59 | 4.4 | 0% | 0 | 578 |
| Oct | 68 | 47 | 3.9 | 51% | 1 | 250 |
| Nov | 57 | 37 | 3.1 | 100% | 10 | 63 |
| Dec | 48 | 30 | 3.7 | 100% | 21 | 15 |
Monthly normals 1991–2020 at Baltimore Wash International Airport, MD (156 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Cylburn, MD, 10 miles northeast of Ellicott City, has a last frost 8 days earlier (April 2), a first frost 7 days later (November 7), a season 16 days longer.
When it snows in Ellicott City, Maryland
The first measurable snow (0.1 inch or more) in Ellicott City usually arrives around December 11, and the last of the season around March 11. Those are the middle dates across the winters of 1991–2020 at Baltimore Wash International Airport, MD, 8.7 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 30 days after the last snow.
Planting calendar for 21043
| When | What to do |
|---|---|
| January 30 – February 13 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 13 – February 27 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 13 – March 27 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 10 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 8 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 17 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 31 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 21043 is 9 miles from Baltimore Wash International Airport, MD, which stands at 156 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 12 other ZIP codes share the station; its figures are presented in full for 21061 (Glen Burnie). The 2023 USDA Plant Hardiness Zone Map lists ZIP 21043 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.