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USDA 2023 hardiness zone · NOAA 1991–2020 frost dates

Frost dates in USDA zone 5b (-15 to -10°F)

USDA zone 5b covers places whose coldest winter night averages -15 to -10°F. Across the 555 NOAA weather stations in zone 5b, the median last spring frost is May 4, but it ranges from Apr 22 to May 26 for most stations. Enter your ZIP for your local date.

  • May 4Median last spring frostmost stations Apr 22–May 26
  • Oct 8Median first fall frost50% chance of 32°F by this date
  • 156 daysMedian growing seasonbetween 32°F freezes
  • 2,880ZIP codes in zone 5b-15 to -10°F average coldest night
  • 555Stations with frost datesof 574 NOAA stations matched

Your ZIP code’s zone and frost dates

Your ZIP gives your zone and the closest NOAA station, which is a better guide than the zone-wide numbers.

5 digits, for example 20001.

From your seed packet, e.g. “start 6 weeks before last frost”.

Earliest and latest last-frost stations in zone 5b

Earliest median last spring frost, zone 5b
StationLast spring frostFirst fall frost
Gladstone Dam 18, ILApr 8Oct 29
Streator 3 SE, ILApr 12Oct 28
Fulton L&d #13, ILApr 13Oct 26
New Boston Dam 17, ILApr 14Oct 24
Valley NWS, NEApr 15Oct 21
Bloomfield, IAApr 16Oct 22
Channahon Dresden Isl Dam, ILApr 16Oct 26
Lamoni, IAApr 16Oct 20
Lamoni Muni Airport, IAApr 16Oct 21
Le Claire L&d 14, IAApr 16Oct 25
Latest median last spring frost, zone 5b
StationLast spring frostFirst fall frost
Vail, COJun 21Sep 7
Boulder 14 W, COJun 21Sep 2
Bellemont WFO, AZJun 21Sep 17
Cimarron, COJun 20Sep 10
Angle, UTJun 17Sep 12
Jiggs 2NE, NVJun 16Sep 13
Fairplay S Park Rd, COJun 16Sep 9
Bailey, COJun 16Sep 8
Grant, COJun 15Sep 9
Mountain View, WYJun 14Sep 9

Zone 5b by state

Zone 5b stations by state
StateStationsMedian last frostMedian first frost
Alaska7May 6Sep 29
Arizona1Jun 21Sep 17
Colorado85May 15Oct 1
Idaho19May 21Sep 20
Illinois55Apr 24Oct 18
Indiana8Apr 25Oct 16
Iowa56Apr 24Oct 14
Maine21May 3Oct 10
Massachusetts9May 6Oct 4
Michigan29May 16Oct 6
Missouri6Apr 19Oct 16
Montana14May 17Sep 25
Nebraska88Apr 30Oct 9
Nevada6Jun 10Sep 14
New Hampshire12May 6Oct 3
New Mexico10May 31Sep 26
New York43May 11Oct 7
Oregon1n/an/a
Pennsylvania13May 15Oct 3
South Dakota3May 12Oct 2
Utah18May 22Sep 25
Vermont6May 10Oct 2
Virginia1May 12Oct 3
West Virginia1May 15Oct 3
Wisconsin53May 1Oct 12
Wyoming9May 21Sep 27

Neighboring zones

  • Zone 5a (-20 to -15°F): median last frost May 9
  • Zone 6a (-10 to -5°F): median last frost May 1

All hardiness zones

How these numbers are made

Each ZIP code gets one zone from the USDA-ARS / PRISM 2023 ZIP tables, which use the map’s 1991–2020 average of the coldest winter night of each year. A ZIP code can span more than one zone, and USDA’s own lookup works by ZIP or address. Each NOAA station is assigned the most common zone among the closest ZIP codes listed on its station page (a tie goes to the zone of the closest of those ZIPs). Frost dates are NOAA’s 50%-probability (median) 32°F dates for each station, the same values shown on the station pages. Zone figures are the median, 10th and 90th percentile across stations; a first fall frost in January to June is counted in the following year.

Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.

Sources

Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.