Frost dates for Conowingo Dam, Maryland
Half of years have their last spring frost by April 3 — but 1 year in 10 still frosts after April 18.
Every other site gives you one date. A frost date is not a date: it is a percentile from 30 years of records at a nearby weather station, and planting to the median means losing the crop in half of years. Both numbers are below, so you can choose the risk yourself.
The odds
Last spring frost
- Frost this late in 1 year in 10
- April 18
- 1 year in 5
- April 14
- 3 years in 10
- April 9
- 2 years in 5
- April 6
- Half of years (the median)
- April 3
First fall freeze
- Freeze this early in 1 year in 10
- October 26
- 1 year in 5
- October 30
- 3 years in 10
- November 1
- 2 years in 5
- November 4
- Half of years (the median)
- November 6
- Growing season
- about 217 days
- Hardiness zones nearby
- 7a, 7b
Where these numbers come from
NOAA NCEI 1991–2020 Climate Normals, station Conowingo Dam (USC00182060), at 39.66, -76.17. These are that station's own records, unshifted. The further your garden is from it, the less exactly they describe your ground — the planner resolves the nearest station to your own ZIP and lowers its confidence with distance, rather than presenting one number as if it were measured in your yard.
Cold air also pools in low ground on the clear, still nights when frost happens, so a hollow can freeze while a slope a hundred metres away does not. No table can know that about your garden. Your own logged frosts eventually can.
ZIP codes nearest this station
17302, 17314, 17321, 17509, 17518, 17532, 17536, 17563, 17566, 19362, 19363, 21001, 21005, 21009, 21013, 21014, 21015, 21017, 21028, 21034, 21040, 21047, 21050, 21051, 21078, 21082, 21084, 21085, 21087, 21130, 21132, 21154, 21156, 21160, 21901, 21902, 21903, 21904, 21911, 21914, 21917, 21918.
What can I plant here, and when? →
Nearby stations
The nearest stations, and how their last-frost dates compare — the frost gradient across your area, which no single station shows.
- Newark Ag Farm Hcn, DE — last frost by April 7
- Lancaster Ap, PA — last frost by April 18
- Millers 4 Ne, MD — last frost by April 19
- Hopewell Morgantown, PA — last frost by April 16
- Baltimore Wash Intl Ap, MD — last frost by April 10
- Middletown Harrisburg Intl Ap, PA — last frost by April 9
Other stations in Maryland.
- Damascus 3 Ssw, MD — last frost by April 14
- Upper Marlboro 3 Nnw, MD — last frost by April 9
- Royal Oak 2 Ssw Hcn, MD — last frost by April 1
- Hagerstown Washington Co Ap, MD — last frost by April 7
- Mechanicsville 5 Ne, MD — last frost by April 17
- Salisbury Hcn, MD — last frost by April 3
- Patuxent River Nas, MD — last frost by March 29
- Cumberland 2 Hcn, MD — last frost by April 15