USDA Hardiness Zone 8a
Frost Dates for 21661 — Rock Hall, Maryland
NOAA 1991–2020 normals from Chestertown, MD (40 ft), 11 miles northeast.
Updated
In Rock Hall, the last spring frost (32°F) is around April 3 in half of years and has passed by April 16 in nine years out of ten. The first fall frost comes around November 5, as early as October 24 one year in ten, leaving a typical freeze-free season of 217 days (NOAA, Chestertown, MD).
- Last spring frost
- April 3
- First fall frost
- November 5
- Growing season
- 217 days
- Hardiness zone
- 8a
50% probability
50% probability
freeze-free, 50%
10 to 15°F (-12.2 to -9.4°C) coldest night
- First snow
- December 27
- Last snow
- March 2
- Winters with snow
- 100%
- Snow per year
- 16.7"
median, 1991–2020
median, 1991–2020
21 of 21 observed
NOAA normal
Frost risk by date in Rock Hall
Half of springs at Chestertown, MD see their last 32°F night by April 3; only one in ten is past it by March 20, and one in ten still has one after April 16. Planting tender crops after April 7 leaves a 30% risk of a frost on them, after April 11 20%, and after April 16 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 80% of the 50 Maryland stations behind this site's ZIP pages.
In fall the first 32°F night comes by November 5 in half of years, as early as October 24 one year in ten, and holds off past November 20 one year in ten. A hard freeze of 28°F follows 12 days later, around November 17; in spring the one-in-ten date for 28°F is April 3, 13 days before the 32°F one. The freeze-free season lasts 217 days in a typical year, longer than at 64% of the 50 Maryland stations; it reaches 237 days one year in ten and falls short of 198 one year in ten. On average 97 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 12 days longer, to about April 15, and return around October 26. Severe cold of 16°F or below comes in 95% of winters, usually between January 5 and February 14.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 1 | Apr 5 | Apr 8 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 25 | Apr 30 |
| 32°F | Mar 20 | Mar 25 | Mar 29 | Mar 31 | Apr 3 | Apr 5 | Apr 7 | Apr 11 | Apr 16 |
| 28°F | Mar 7 | Mar 12 | Mar 15 | Mar 18 | Mar 21 | Mar 24 | Mar 27 | Mar 31 | Apr 3 |
| 24°F | Feb 23 | Feb 28 | Mar 3 | Mar 7 | Mar 10 | Mar 13 | Mar 16 | Mar 19 | Mar 23 |
| 20°F | Feb 5 | Feb 13 | Feb 19 | Feb 24 | Feb 28 | Mar 2 | Mar 5 | Mar 9 | Mar 15 |
| 16°F95% of yrs | Jan 18 | Jan 29 | Feb 3 | Feb 9 | Feb 14 | Feb 18 | Feb 24 | Feb 28 | Mar 5 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 12 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 3 | Nov 8 |
| 32°F | Oct 24 | Oct 29 | Nov 1 | Nov 3 | Nov 5 | Nov 8 | Nov 11 | Nov 15 | Nov 20 |
| 28°F | Nov 5 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 21 | Nov 24 | Nov 29 | Dec 5 |
| 24°F | Nov 13 | Nov 18 | Nov 22 | Nov 28 | Dec 1 | Dec 5 | Dec 10 | Dec 17 | Dec 23 |
| 20°F | Nov 29 | Dec 4 | Dec 10 | Dec 16 | Dec 21 | Dec 26 | Dec 31 | Jan 4 | Jan 12 |
| 16°F95% of yrs | Dec 14 | Dec 22 | Dec 28 | Jan 1 | Jan 5 | Jan 10 | Jan 15 | Jan 23 | Feb 1 |
Freeze probabilities 1991–2020 at Chestertown, 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 21661 →Compare Rock Hall with another place →
Weather by month in Rock Hall
July is the warmest month at Chestertown, MD, averaging 87°F by day and 69°F at night; January is the coldest at 41°F and 27°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 59% of years.
Warmth for growing adds up to 3,938 growing degree days a year (base 50°F), more than at 56% of the 50 Maryland stations. 35% of them (1,372) have built up by the end of June, and July adds the most, 857. Precipitation totals 46.1 inches a year, most in September (4.9") 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 | 41 | 27 | 3.3 | 100% | 25 | 7 |
| Feb | 44 | 28 | 2.9 | 100% | 22 | 6 |
| Mar | 53 | 35 | 4.3 | 100% | 15 | 39 |
| Apr | 64 | 45 | 3.7 | 59% | 2 | 185 |
| May | 74 | 55 | 3.9 | 0% | 0 | 443 |
| Jun | 82 | 64 | 4.4 | 0% | 0 | 693 |
| Jul | 87 | 69 | 4.4 | 0% | 0 | 857 |
| Aug | 85 | 67 | 3.6 | 0% | 0 | 809 |
| Sep | 78 | 60 | 4.9 | 0% | 0 | 577 |
| Oct | 67 | 48 | 3.7 | 28% | 1 | 248 |
| Nov | 56 | 38 | 3.2 | 98% | 10 | 61 |
| Dec | 45 | 31 | 3.8 | 100% | 23 | 13 |
Monthly normals 1991–2020 at Chestertown, MD (40 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, Stevensville 2SW, MD, 13 miles southwest of Rock Hall, has a last frost 5 days earlier (March 29), a first frost 7 days later (November 12), a season 11 days longer.
When it snows in Rock Hall, Maryland
The first measurable snow (0.1 inch or more) in Rock Hall usually arrives around December 27, and the last of the season around March 2. Those are the middle dates across the winters of 1991–2020 at Chestertown, MD, 10.9 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 32 days after the last snow.
Planting calendar for 21661
| When | What to do |
|---|---|
| January 23 – February 6 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 6 – February 20 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 6 – March 20 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 3 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 13 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 22 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 5 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 21661 is 11 miles from Chestertown, MD, which stands at 40 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 21620 (Chestertown). The 2023 USDA Plant Hardiness Zone Map lists ZIP 21661 in zone 8a, the band where the coldest night of the year averaged 10 to 15°F (-12.2 to -9.4°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.