Frost dates / Massachusetts / Waltham

Frost dates in Waltham, MA

The station on this page is BEDFORD HANSCOM FLD, MA US (USW00014702), 6.1 miles from the city point. Population in the Census 2024 estimate is 65,849.

Zone 6bUSDA average annual extreme minimum -5°F to 0°F, from ZIP 02451 (1 miles from the city point used on this page).

Median last 32°F is April 28. Median first 32°F is October 10. The 50% growing-season length is 165 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%	April 13	Earlier date. A last 32°F on or after this day is common.
50%	April 28	Median.
10%	May 12	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%	September 28	Earlier date. A first 32°F on or before this day is uncommon.
50%	October 10	Median.
90%	October 28	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%	186
50%	165
90%	146

28°F threshold

	10%	50%	90%
Last, on or after	April 29	April 12	April 1
First, on or before	October 7	October 25	November 8
Season at least	214 days	194 days	171 days

36°F threshold

	10%	50%	90%
Last, on or after	May 23	May 10	April 28
First, on or before	September 17	October 1	October 13
Season at least	160 days	143 days	125 days

Station BEDFORD HANSCOM FLD, MA US (USW00014702). Completeness flag R, 20 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 40.5 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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Waltham, MA

Zone 6bAverage annual extreme minimum -5°F to 0°F

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

Massachusetts. Nearest qualified station: BEDFORD HANSCOM FLD, MA US (USW00014702), 6.1 miles. Median last 32°F April 28. Median first 32°F October 10. The 50% growing-season length is 165 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	May 12	April 28	April 13
First 32°F on or before	September 28	October 10	October 28

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 Massachusetts 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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