Which frost date do the crop weeks use?

Weeks after the frost-free date use the median last 32°F date, April 22, when the guide does not name a probability. Weeks before the first freeze use the median first 32°F date, October 18. Both medians are 50% dates in the NOAA 1991–2020 normals for the station on this page. The page says when that anchor was used.

Where do the crop dates come from?

Crop dates come from the extension guide cited on this page, not from a second calendar invented here. The publisher and the title are printed with the source note. A month without a day is expanded to the first and last day of that month, and the page says so. A phrase without two dates stays a phrase.

Is this planting calendar a forecast?

No. The frost dates are 1991–2020 climate normals at the station 2.5 miles from the city point. The crop windows are the cited guide’s ranges, shifted only when that guide itself used weeks. A cold spring can still fall past the median. The National Weather Service forecast covers a particular night. This page does not.

Planting calendar for Fairfield, OH

Direct answer. In Fairfield, OH, the median last 32°F date at HAMILTON BUTLER CO RGNL AP, OH US (USW00053855) is April 22, and the median first 32°F date is October 18. The station is 2.5 miles from the city point. Crop windows come from Ohio State University Extension. Where that guide counts weeks from a frost date and does not name a 10%, 50%, or 90% level, those weeks are applied to these median dates.

Median last 32°F April 22. Median first 32°F October 18. Frost dates for Fairfield.

A wall calendar surrounded by vegetables, herbs, seed packets, and watering cans.

Median last 32°F is April 22. Median first 32°F is October 18. The 50% growing-season length is 178 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 6	Earlier date. A last 32°F on or after this day is common.
50%	April 22	Median.
10%	May 10	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 5	Earlier date. A first 32°F on or before this day is uncommon.
50%	October 18	Median.
90%	October 29	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%	198
50%	178
90%	157

28°F threshold

	10%	50%	90%
Last, on or after	April 28	April 8	March 26
First, on or before	October 15	October 27	November 8
Season at least	221 days	200 days	178 days

36°F threshold

	10%	50%	90%
Last, on or after	May 19	May 2	April 18
First, on or before	September 25	October 7	October 20
Season at least	177 days	159 days	138 days

Station HAMILTON BUTLER CO RGNL AP, OH US (USW00053855). Completeness flag R, 21 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 193.2 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

Questions

Which frost date do the crop weeks use?: Weeks after the frost-free date use the median last 32°F date, April 22, when the guide does not name a probability. Weeks before the first freeze use the median first 32°F date, October 18. Both medians are 50% dates in the NOAA 1991–2020 normals for the station on this page. The page says when that anchor was used.
Where do the crop dates come from?: Crop dates come from the extension guide cited on this page, not from a second calendar invented here. The publisher and the title are printed with the source note. A month without a day is expanded to the first and last day of that month, and the page says so. A phrase without two dates stays a phrase.
Is this planting calendar a forecast?: No. The frost dates are 1991–2020 climate normals at the station 2.5 miles from the city point. The crop windows are the cited guide’s ranges, shifted only when that guide itself used weeks. A cold spring can still fall past the median. The National Weather Service forecast covers a particular night. This page does not.

Crops in the cited guide

Fairfield, OH

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

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

Ohio. Nearest qualified station: HAMILTON BUTLER CO RGNL AP, OH US (USW00053855), 2.5 miles. Median last 32°F April 22. Median first 32°F October 18. The 50% growing-season length is 178 days.

Open the ZIP page · Crop guides for Ohio

32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	May 10	April 22	April 6
First 32°F on or before	October 5	October 18	October 29

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.

Planting calendar

Windows below are from Ohio State University Extension, Planning for the Garden, excerpted from OSU Extension Bulletin 287, Home Vegetable Gardening, retrieved 2026-10-10. The dates are for a normal season in central Ohio. The same page says spring planting runs about two weeks earlier in southern Ohio and about two weeks later in northern Ohio. Those shifts are a sentence, not a second column, so the dates below stay the central Ohio dates. The PDF says the tables are excerpted from Bulletin 287 by Utzinger, Brooks and Wittmeyer, 1991, now out of print.

Crop

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State crop pages: Beans, bush snap · Beets · Collards · Corn, Sweet · Cucumber · Kale · Lettuce, leaf · Okra