USDA Hardiness Zone 7a
Frost Dates for 21783 — Smithsburg, Maryland
NOAA 1991–2020 normals from Smithsburg 2NW, MD (670 ft), 1 miles northwest.
Updated
In Smithsburg, the last spring frost (32°F) is around April 25 in half of years and has passed by May 11 in nine years out of ten. The first fall frost comes around October 19, as early as October 6 one year in ten, leaving a typical freeze-free season of 176 days (NOAA, Smithsburg 2NW, MD).
- Last spring frost
- April 25
- First fall frost
- October 19
- Growing season
- 176 days
- Hardiness zone
- 7a
50% probability
50% probability
freeze-free, 50%
0 to 5°F (-17.8 to -15.0°C) coldest night
- First snow
- December 17
- Last snow
- March 5
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
19 of 19 observed
NOAA normal
Frost risk by date in Smithsburg
Half of springs at Smithsburg 2NW, MD see their last 32°F night by April 25; only one in ten is past it by April 12, and one in ten still has one after May 11. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 5 20%, and after May 11 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 50% of the 50 Maryland stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 19 in half of years, as early as October 6 one year in ten, and holds off past November 3 one year in ten. A hard freeze of 28°F follows 11 days later, around October 30; in spring the one-in-ten date for 28°F is April 27, 14 days before the 32°F one. The freeze-free season lasts 176 days in a typical year, shorter than at 86% of the 50 Maryland stations; it reaches 198 days one year in ten and falls short of 155 one year in ten. On average 122 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 10 days longer, to about May 5, and return around October 8. Severe cold of 16°F or below comes every winter, usually between December 9 and March 8.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 23 | Apr 27 | Apr 30 | May 2 | May 5 | May 8 | May 12 | May 16 | May 22 |
| 32°F | Apr 12 | Apr 16 | Apr 19 | Apr 22 | Apr 25 | Apr 28 | May 1 | May 5 | May 11 |
| 28°F | Mar 30 | Apr 3 | Apr 6 | Apr 9 | Apr 11 | Apr 14 | Apr 17 | Apr 21 | Apr 27 |
| 24°F | Mar 15 | Mar 22 | Mar 26 | Mar 29 | Apr 1 | Apr 3 | Apr 6 | Apr 9 | Apr 14 |
| 20°F | Mar 2 | Mar 8 | Mar 12 | Mar 15 | Mar 19 | Mar 23 | Mar 27 | Mar 30 | Apr 3 |
| 16°F | Feb 19 | Feb 25 | Mar 1 | Mar 5 | Mar 8 | Mar 11 | Mar 14 | Mar 18 | Mar 24 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 26 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 18 | Oct 22 |
| 32°F | Oct 6 | Oct 10 | Oct 14 | Oct 16 | Oct 19 | Oct 22 | Oct 25 | Oct 29 | Nov 3 |
| 28°F | Oct 15 | Oct 21 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 5 | Nov 8 | Nov 14 |
| 24°F | Oct 26 | Oct 31 | Nov 3 | Nov 7 | Nov 10 | Nov 14 | Nov 18 | Nov 23 | Nov 30 |
| 20°F | Nov 6 | Nov 11 | Nov 16 | Nov 20 | Nov 25 | Nov 29 | Dec 3 | Dec 8 | Dec 15 |
| 16°F | Nov 18 | Nov 25 | Dec 1 | Dec 5 | Dec 9 | Dec 15 | Dec 19 | Dec 24 | Dec 31 |
Freeze probabilities 1991–2020 at Smithsburg 2NW, 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 21783 →Compare Smithsburg with another place →
Weather by month in Smithsburg
July is the warmest month at Smithsburg 2NW, MD, averaging 86°F by day and 63°F at night; January is the coldest at 39°F and 22°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 32% of years.
Warmth for growing adds up to 3,218 growing degree days a year (base 50°F), fewer than at 88% of the 50 Maryland stations. 34% of them (1,110) have built up by the end of June, and July adds the most, 749.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 39 | 22 | 100% | 25 | 4 |
| Feb | 42 | 22 | 100% | 24 | 5 |
| Mar | 51 | 29 | 100% | 21 | 27 |
| Apr | 63 | 39 | 99% | 7 | 132 |
| May | 72 | 49 | 32% | 1 | 344 |
| Jun | 81 | 59 | 0% | 0 | 598 |
| Jul | 86 | 63 | 0% | 0 | 749 |
| Aug | 84 | 61 | 0% | 0 | 693 |
| Sep | 77 | 54 | 0% | 0 | 461 |
| Oct | 66 | 42 | 85% | 3 | 172 |
| Nov | 53 | 32 | 100% | 16 | 27 |
| Dec | 43 | 26 | 100% | 24 | 6 |
Monthly normals 1991–2020 at Smithsburg 2NW, MD (670 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, Catoctin Mountain Park, MD, 5 miles east of Smithsburg and 940 feet higher, has a last frost 11 days earlier (April 14), a first frost 11 days later (October 30), a season 21 days longer.
When it snows in Smithsburg, Maryland
The first measurable snow (0.1 inch or more) in Smithsburg usually arrives around December 17, and the last of the season around March 5. Those are the middle dates across the winters of 1991–2020 at Catoctin Mountain Park, MD, 4.5 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 51 days after the last snow.
Planting calendar for 21783
| When | What to do |
|---|---|
| February 14 – February 28 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 28 – March 14 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 28 – April 11 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 25 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 27 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 5 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 19 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 21783 is 1 mile from Smithsburg 2NW, MD, which stands at 670 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 21783 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°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.