When to Plant Sweet corn

Enter your ZIP code to see the sweet corn planting windows from the frost dates at the nearest weather station. The rules below come from university extension publications and count from the average last or first frost.

Your area

Risk level

How much frost risk you'll accept. Each level uses the frost dates with this chance of a frost after the last-frost date or before the first-frost date: Conservative 10%, Typical 30%, Aggressive 50%.

Planting year

The year the frost dates and windows are placed on.

Sweet corn planting windows

Sweet corn planting rules

Each rule counts days or weeks from the average last spring frost or first fall frost in its source. YepPlant applies the same count to the 32°F frost dates at each risk level: Conservative (10%), Typical (30%), and Aggressive (50%). A range in a rule becomes a range in the window. Where sources differ or don't give a single value, the value is YepPlant's reading of the sources, and it stays within what they say.

Sweet corn planting rules, from university extension publications
Rule	Value	Sources
Frost threshold	32°F frost dates	—
Transplant outdoors	Not available	—
Start seeds indoors	Not available	—
Sow outdoors	On the last spring frost date	CSU, USU
Days to maturity from sowing	60 to 90 days	CSU, UMD-P, NCSUYepPlant's reading of these sources
Frost Tender Factor	14 days: the crop should mature at least this long before the first fall frost	UNLYepPlant's reading of these sources
Last sowing date	First fall frost − days to maturity from sowing − Frost Tender Factor	PUR, NCSU, UNLYepPlant's reading of these sources
Fall planting	Not available	—
Crop rotation	Plant this crop's family in the same spot at most once every 3 years	NCSU

Not available means no rule from the sources is used for it, so no window depends on it. Rows without a source follow the rules shared by all crops, described on the methods and sources page.

Sources

University extension publications, with the date each was retrieved. The frost dates come from NOAA's 1991–2020 Climate Normals at the weather station nearest your ZIP code, and the station is found from the Census Bureau's ZIP Code Tabulation Areas.

CSU: Colorado State University Extension, GardenNotes #720: Vegetable Planting Guide: Used for: Sow outdoors, Days to maturity from sowing. Retrieved October 13, 2026.
USU: Utah State University Extension: Suggested Vegetable Planting Dates for Utah: Used for: Sow outdoors. Retrieved October 13, 2026.
UMD-P: University of Maryland Extension: Vegetables for Spring and Fall Planting: Used for: Days to maturity from sowing. Retrieved October 13, 2026.
NCSU: NC State Extension, Extension Gardener Handbook Chapter 16: Vegetable Gardening: Used for: Days to maturity from sowing, Last sowing date, Crop rotation. Retrieved October 13, 2026.
CLEM: Clemson Cooperative Extension, HGIC 1259: Starting Seeds Indoors: Consulted, but no rule on this page comes from it. Retrieved October 13, 2026.
UMD-S: University of Maryland Extension HGIC: Starting Vegetable Seeds Indoors: Consulted, but no rule on this page comes from it. Retrieved October 13, 2026.
PUR: Purdue Extension, HO-66-W: The Fall Vegetable Garden: Used for: Last sowing date. Retrieved October 13, 2026.
UNL: Nebraska Extension, NebGuide G1343: Fall Vegetable Gardening: Used for: Frost Tender Factor, Last sowing date. Retrieved October 13, 2026.

Data sources

NOAA U.S. Climate Normals, frost dates, 1991–2020 normals, version 1.0.1: Files: us-climate-normals_1991-2020_v1.0.1_annualseasonal_multivariate_by-station_c20230404.tar.gz, inventory_30yr.txt from NOAA NCEI. Retrieved October 10, 2026.
U.S. Census Bureau ZIP Code Tabulation Areas, 2026 Gazetteer Files and 2020 ZCTA to County Relationship File: Files: 2026_Gaz_zcta_national.zip, tab20_zcta520_county20_natl.txt, national_state2020.txt from the U.S. Census Bureau. Retrieved October 10, 2026.