Frost Dates for 21218 — Baltimore, Maryland

Half of springs at Md Sci Ctr Baltimore, MD see their last 32°F night by March 24; only one in ten is past it by March 8, and one in ten still has one after April 4. Planting tender crops after March 29 leaves a 30% risk of a frost on them, after April 1 20%, and after April 4 10%. The 11 days between the even-odds date and the one-in-ten date is narrower than at 94% of the 50 Maryland stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 21 in half of years, as early as November 7 one year in ten, and holds off past December 8 one year in ten. A hard freeze of 28°F follows 14 days later, around December 5; in spring the one-in-ten date for 28°F is March 26, 9 days before the 32°F one. The freeze-free season lasts 244 days in a typical year, longer than at 98% of the 50 Maryland stations; it reaches 268 days one year in ten and falls short of 224 one year in ten. On average 52 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 April 3, and return around November 10. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 81%.

July is the warmest month at Md Sci Ctr Baltimore, MD, averaging 90°F by day and 73°F at night; January is the coldest at 44°F and 30°F. A freezing night is all but certain in every month from December to March (a 90% chance or more). From May to October the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 21% of years.

Warmth for growing adds up to 4,686 growing degree days a year (base 50°F), the most of the 50 Maryland stations. 36% of them (1,673) have built up by the end of June, and July adds the most, 976. Precipitation totals 44.0 inches a year, most in July (4.7") and least in February (2.8"); May to September bring 46% of it.

The nearest other station, Cylburn, MD, 3 miles northwest of Baltimore and 215 feet higher, has a last frost 9 days later (April 2), a first frost 14 days earlier (November 7), a season 24 days shorter.

The first measurable snow (0.1 inch or more) in Baltimore 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, 11.8 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 13 days after the last snow.

ZIP 21218 is 3 miles from Md Sci Ctr Baltimore, MD, which stands at 20 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 21 other ZIP codes share the station; its figures are presented in full for 21222 (Dundalk). The 2023 USDA Plant Hardiness Zone Map lists ZIP 21218 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.