Frost dates / Maryland / Rockville

Frost dates in Rockville, MD

The station on this page is ROCKVILLE 1 NE, MD US (USC00187705), 1.2 miles from the city point. Population in the Census 2024 estimate is 68,417.

Zone 7bUSDA average annual extreme minimum 5°F to 10°F, from ZIP 20850 (1.4 miles from the city point used on this page).

Median last 32°F is April 1. Median first 32°F is November 6. The 50% growing-season length is 219 days. The green band runs from the median last frost to the median first frost. Thin ticks mark the 10%, 50%, and 90% dates.

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Last 32°F in spring

NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.

Probability	Date	How to read it
90%	March 19	Earlier date. A last 32°F on or after this day is common.
50%	April 1	Median.
10%	April 15	Later date. A last 32°F on or after this day is uncommon.

First 32°F in fall

NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.

Probability	Date	How to read it
10%	October 24	Earlier date. A first 32°F on or before this day is uncommon.
50%	November 6	Median.
90%	November 21	Later date. A first 32°F on or before this day is common.

32°F growing-season length

Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.

Probability the season is at least this long	Days
10%	240
50%	219
90%	200

28°F threshold

	10%	50%	90%
Last, on or after	April 4	March 22	March 5
First, on or before	November 5	November 19	December 6
Season at least	267 days	243 days	224 days

36°F threshold

	10%	50%	90%
Last, on or after	May 5	April 16	March 31
First, on or before	October 12	October 25	November 7
Season at least	212 days	192 days	170 days

Station ROCKVILLE 1 NE, MD US (USC00187705). Completeness flag R, 14 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 134.1 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

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Rockville, MD

Zone 7bAverage annual extreme minimum 5°F to 10°F

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Maryland. Nearest qualified station: ROCKVILLE 1 NE, MD US (USC00187705), 1.2 miles. Median last 32°F April 1. Median first 32°F November 6. The 50% growing-season length is 219 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	April 15	April 1	March 19
First 32°F on or before	October 24	November 6	November 21

Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.

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Planting calendar

Frost dates for Maryland are above. Planting windows appear for states with a cited extension guide. The fall and seed tools use the numbers you enter and the station dates.

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