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.
A frost date is really a percentile from 30 years of records at a nearby weather station: in about half of years a frost still comes after the median date. Both numbers are below, so you can choose the risk yourself.
The odds
Last spring frost
How often a frost still comes on or after each date.
- 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
How often the first freeze comes on or before each date.
- 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
- Summer days
- a usual high of about 30 °C85 °F
- Lettuce and spinach run to seed
- June to September, in hot, long days (how we know)
Summer and rain
A growing garden needs about 25 mm1 in of water a week, rain and watering together. Here is what a normal month brings.
Month by month
- January
- high ~4 °C40 °F · low ~-4 °C25 °F · rain ~92 mm3.6 in
- February
- high ~6 °C43 °F · low ~-3 °C26 °F · rain ~67 mm2.6 in
- March
- high ~11 °C51 °F · low ~1 °C34 °F · rain ~106 mm4.2 in
- April
- high ~18 °C64 °F · low ~7 °C44 °F · rain ~87 mm3.4 in
- May
- high ~23 °C74 °F · low ~12 °C54 °F · rain ~98 mm3.9 in
- June
- high ~28 °C83 °F · low ~18 °C64 °F · rain ~113 mm4.5 in
- July
- high ~31 °C87 °F · low ~20 °C69 °F · rain ~119 mm4.7 in
- August
- high ~30 °C85 °F · low ~19 °C67 °F · rain ~115 mm4.5 in
- September
- high ~26 °C79 °F · low ~16 °C60 °F · rain ~128 mm5.1 in
- October
- high ~19 °C67 °F · low ~9 °C48 °F · rain ~114 mm4.5 in
- November
- high ~13 °C55 °F · low ~3 °C37 °F · rain ~82 mm3.2 in
- December
- high ~7 °C45 °F · low ~-1 °C31 °F · rain ~103 mm4 in
Where these numbers come from
NOAA NCEI 1991–2020 Climate Normals, the Conowingo Dam station (listed by NOAA as 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 finds the nearest station to your garden and lowers its confidence with distance, so no number is presented as if it were measured in your garden.
Cold air also pools in low ground on the clear, still nights when frost happens, so a hollow can freeze while a slope a few hundred feet away does not. No table can know that about your garden. A few seasons of your own logged frosts can.
ZIP codes nearest this station
17314, 17563, 21028, 21034, 21050, 21084, 21132, 21154, 21160, 21901, 21903, 21904…
+3 moreShow fewer
21914, 21917, 21918.
Nearby stations
The nearest stations and how their last-frost dates compare. Together they show how frost varies across your area.
- Newark Ag Farm, DE, last frost by April 7
- Lancaster Airport, PA, last frost by April 18
- Cylburn, MD, last frost by April 2
- Millers 4 NE, MD, last frost by April 19
- Baltimore Wash International Airport, MD, last frost by April 10
- Middletown Harrisburg International Airport, 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, MD, last frost by April 1
- Dalecarlia Rsvr, MD, last frost by April 9
- Hagerstown Washington County Airport, MD, last frost by April 7
- Mechanicsville 5 NE, MD, last frost by April 17
- Salisbury, MD, last frost by April 3
- Patuxent River Naval Air Station, MD, last frost by March 29
When do I plant? · Where the dates come from
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