USDA hardiness zone 5b
In zone 5b, the average annual extreme minimum temperature is -15 to -10°F (-26.1 to -23.3°C), based on 1991–2020 data from the 2023 USDA Plant Hardiness Zone Map.
What zone 5b means for your garden
A plant labeled "hardy to zone 5b" should survive a typical winter low of -15°F. Most perennials sold at garden centers are rated for this zone or colder; marginal plants rated one zone warmer can survive in sheltered spots. Zone 5a is the colder half of zone 5.
ZIP codes in zone 5b: 2,865 in contiguous U.S., 15 in Alaska. New to zones? Read how to read your hardiness zone.
Frost dates in zone 5b
Across 21 major cities in zone 5b, the 30%-risk last spring frost ranges from Apr 24 to May 22 (median May 4), and the first fall frost has a median of Oct 9. Frost timing depends on elevation, latitude and distance from water — a zone does not set a frost date, so check your city page for local dates.
Typical planting calendar for zone 5b
Based on the median frost dates above. For your exact dates, use your city page.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Mar 9 – Mar 23 | May 11 – May 25 | — | — |
| Pepper | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Lettuce | Mar 23 – Apr 6 | Apr 20 – May 11 | Apr 6 – May 18 | Jul 31 – Aug 28 |
| Green Beans | — | — | May 11 – Jun 15 | Jul 17 – Jul 31 |
| Sweet Corn | — | — | May 11 – Jun 8 | — |
| Zucchini & Summer Squash | Apr 6 – Apr 13 | May 11 – May 25 | May 11 – Jun 1 | Jul 17 – Jul 31 |
| Cucumber | Apr 6 – Apr 13 | May 18 – May 25 | May 11 – Jun 1 | Jul 17 – Jul 31 |
| Carrot | — | — | Apr 13 – May 18 | Jul 17 – Jul 31 |
| Onion | Feb 9 – Feb 23 | Apr 6 – Apr 20 | — | — |
| Potato | — | Apr 6 – Apr 27 | — | — |
| Basil | Mar 23 – Apr 6 | May 18 – Jun 1 | May 18 – Jun 8 | — |
| Spinach | — | — | Mar 23 – Apr 20 | Aug 14 – Sep 11 |
| Kale | Mar 9 – Mar 23 | Apr 6 – Apr 27 | Apr 6 – Apr 27 | Jul 31 – Aug 28 |
| Broccoli | Mar 9 – Mar 23 | Apr 20 – May 11 | — | Jul 17 – Jul 31 |
| Peas | — | — | Mar 23 – Apr 13 | Jul 31 – Aug 14 |
| Eggplant | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Cabbage | Mar 9 – Mar 23 | Apr 6 – Apr 20 | — | Jul 17 – Jul 31 |
| Radish | — | — | Mar 30 – May 18 | Aug 28 – Sep 25 |
| Strawberry | — | Apr 6 – Apr 27 | — | — |
| Beets | — | — | Apr 13 – May 25 | Jul 31 – Aug 14 |
Cities in zone 5b (21)
Major cities whose center falls in zone 5b:
- Madison, WI — last frost May 7, first frost Oct 3
- Des Moines, IA — last frost Apr 24, first frost Oct 14
- Aurora, IL — last frost Apr 25, first frost Oct 18
- Fort Collins, CO — last frost May 7, first frost Oct 2
- Naperville, IL — last frost May 4, first frost Oct 11
- Rockford, IL — last frost Apr 30, first frost Oct 12
- Elgin, IL — last frost May 1, first frost Oct 12
- Greeley, CO — last frost May 7, first frost Oct 3
- Green Bay, WI — last frost May 13, first frost Oct 2
- Davenport, IA — last frost Apr 24, first frost Oct 17
- Longmont, CO — last frost May 13, first frost Oct 1
- Kenosha, WI — last frost May 3, first frost Oct 14
- Castle Rock, CO — last frost May 15, first frost Sep 27
- Loveland, CO — last frost May 15, first frost Sep 25
- Missoula, MT — last frost May 22, first frost Sep 20
- Schaumburg, IL — last frost May 6, first frost Oct 8
- Ankeny, IA — last frost Apr 29, first frost Oct 9
- Iowa City, IA — last frost Apr 28, first frost Oct 13
- Lewiston, ME — last frost Apr 30, first frost Oct 13
- Burlington, VT — last frost May 3, first frost Oct 9
- Cheyenne, WY — last frost May 20, first frost Sep 26
← Zone 5a · Zone 6a → · All zones
Zone 5b questions
How cold does it get in zone 5b?
Zone 5b is defined by an average annual extreme minimum temperature of -15 to -10°F (-26.1 to -23.3°C) for 1991–2020 — the average of each year's single coldest night, not the record low. Individual winters can be colder, so plants rated exactly for zone 5b carry some risk in a severe year.
When is the last frost in zone 5b?
It depends far more on the city than on the zone. Among 21 zone 5b cities on this site, the 30%-risk last spring frost runs from Apr 24 in Des Moines, IA to May 22 in Missoula, MT — 28 days apart (median May 4).
Which states have zone 5b?
The 2023 listings put 2,880 ZIP codes in zone 5b, spread over 26 states and territories. The most are in Illinois (447), New York (436), Iowa (425), Nebraska (291), Wisconsin (263).
Did zone 5b grow on the 2023 map?
No: 4,781 ZIP codes were in zone 5b on the 2012 map and 2,880 are on the 2023 map (-1,901). Of today's zone 5b ZIP codes that were also listed in 2012, 38% were in a colder zone then, 61% were already 5b, and 1% were in a warmer zone. What changed in 2023.
Which big cities are in zone 5b?
The largest cities on this site in zone 5b are Madison, WI, Des Moines, IA, Aurora, IL; 21 cities in all are listed below.