What USDA zone is Waterloo, IA?

The zone on this page is 5a, from ZIP 50702 in the 2023 PRISM table of the USDA Plant Hardiness Zone Map. That ZIP is 2.9 miles from the city point. USDA defines the zone as the average annual extreme minimum, shown here as -20°F to -15°F. It is a winter-cold band, not a frost date and not a forecast.

How far away is the weather station?

The station named on this page is 5 miles from the city point in a straight line. Frost dates are 1991–2020 NOAA climate normals for that instrument. They are not a National Weather Service forecast for one night, and they are not the temperature in every yard. The page names the station so the miles stay attached to the dates.

Frost dates in Waterloo, IA

Direct answer. In Waterloo, IA, the nearest qualified NOAA station is WATERLOO MUNI AP, IA US (USW00094910), 5 miles from the city point. The median last 32°F date is April 27, and the median first 32°F date is October 10, from the 1991–2020 U.S. Climate Normals. The 2023 USDA zone is 5a (-20°F to -15°F), from ZIP 50702 in the PRISM table, 2.9 miles from the same city point.

Population in the Census 2024 estimate is 67,477. The station is WATERLOO MUNI AP, IA US (USW00094910).

Zone 5aUSDA average annual extreme minimum -20°F to -15°F, from ZIP 50702 (2.9 miles from the city point used on this page).

Median last 32°F is April 27. 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 11	Earlier date. A last 32°F on or after this day is common.
50%	April 27	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%	September 26	Earlier date. A first 32°F on or before this day is uncommon.
50%	October 10	Median.
90%	October 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%	184
50%	165
90%	146

28°F threshold

	10%	50%	90%
Last, on or after	May 2	April 16	April 3
First, on or before	October 6	October 20	October 31
Season at least	204 days	185 days	165 days

36°F threshold

	10%	50%	90%
Last, on or after	May 17	May 6	April 23
First, on or before	September 16	September 30	October 11
Season at least	166 days	147 days	129 days

Station WATERLOO MUNI AP, IA US (USW00094910). Completeness flag S, 30 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 264.6 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

Questions

When is the last spring frost in Waterloo, IA?: The median last 32°F date at the station on this page is April 27. NOAA’s 1991–2020 normals give a 50% chance the last spring minimum of 32°F or lower occurs on or after that date. The 90% date is April 11. The 10% date, the later one, is May 10. These are normals, not a forecast for this spring.
What USDA zone is Waterloo, IA?: The zone on this page is 5a, from ZIP 50702 in the 2023 PRISM table of the USDA Plant Hardiness Zone Map. That ZIP is 2.9 miles from the city point. USDA defines the zone as the average annual extreme minimum, shown here as -20°F to -15°F. It is a winter-cold band, not a frost date and not a forecast.
How far away is the weather station?: The station named on this page is 5 miles from the city point in a straight line. Frost dates are 1991–2020 NOAA climate normals for that instrument. They are not a National Weather Service forecast for one night, and they are not the temperature in every yard. The page names the station so the miles stay attached to the dates.

Check a crop against this station

Waterloo, IA

Zone 5aAverage annual extreme minimum -20°F to -15°F

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

Iowa. Nearest qualified station: WATERLOO MUNI AP, IA US (USW00094910), 5 miles. Median last 32°F April 27. Median first 32°F October 10. The 50% growing-season length is 165 days.

Open the ZIP page

32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	May 10	April 27	April 11
First 32°F on or before	September 26	October 10	October 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.

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

Planting calendar

Frost dates for Iowa 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.

Date checks use your device’s calendar and appear after the page loads.