USDA hardiness zone 5a
In zone 5a, the average annual extreme minimum temperature is -20 to -15°F (-28.9 to -26.1°C), based on 1991–2020 data from the 2023 USDA Plant Hardiness Zone Map.
What zone 5a means for your garden
A plant labeled "hardy to zone 5a" should survive a typical winter low of -20°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 5b is the warmer half of zone 5.
ZIP codes in zone 5a: 2,393 in contiguous U.S., 33 in Alaska. New to zones? Read how to read your hardiness zone.
Frost dates in zone 5a
Across 14 major cities in zone 5a, the 30%-risk last spring frost ranges from Apr 30 to May 16 (median May 4), and the first fall frost has a median of Oct 3. 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 5a
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 25 – Aug 22 |
| Green Beans | — | — | May 11 – Jun 15 | Jul 11 – Jul 25 |
| Sweet Corn | — | — | May 11 – Jun 8 | — |
| Zucchini & Summer Squash | Apr 6 – Apr 13 | May 11 – May 25 | May 11 – Jun 1 | Jul 11 – Jul 25 |
| Cucumber | Apr 6 – Apr 13 | May 18 – May 25 | May 11 – Jun 1 | Jul 11 – Jul 25 |
| Carrot | — | — | Apr 13 – May 18 | Jul 11 – Jul 25 |
| 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 8 – Sep 5 |
| Kale | Mar 9 – Mar 23 | Apr 6 – Apr 27 | Apr 6 – Apr 27 | Jul 25 – Aug 22 |
| Broccoli | Mar 9 – Mar 23 | Apr 20 – May 11 | — | Jul 11 – Jul 25 |
| Peas | — | — | Mar 23 – Apr 13 | Jul 25 – Aug 8 |
| Eggplant | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Cabbage | Mar 9 – Mar 23 | Apr 6 – Apr 20 | — | Jul 11 – Jul 25 |
| Radish | — | — | Mar 30 – May 18 | Aug 22 – Sep 19 |
| Strawberry | — | Apr 6 – Apr 27 | — | — |
| Beets | — | — | Apr 13 – May 25 | Jul 25 – Aug 8 |
Cities in zone 5a (14)
Major cities whose center falls in zone 5a:
- Minneapolis, MN — last frost Apr 30, first frost Oct 10
- St. Paul, MN — last frost May 1, first frost Oct 7
- Anchorage, AK — last frost May 4, first frost Sep 24
- Sioux Falls, SD — last frost May 6, first frost Sep 30
- Cedar Rapids, IA — last frost May 3, first frost Oct 5
- Billings, MT — last frost May 11, first frost Sep 28
- Bloomington, MN — last frost Apr 30, first frost Oct 11
- Sioux City, IA — last frost May 4, first frost Oct 1
- Brooklyn Park, MN — last frost May 6, first frost Oct 2
- Woodbury, MN — last frost May 1, first frost Oct 5
- Rapid City, SD — last frost May 9, first frost Oct 1
- Plymouth, MN — last frost May 4, first frost Oct 5
- South Burlington, VT — last frost May 3, first frost Oct 9
- Casper, WY — last frost May 16, first frost Sep 23
← Zone 4b · Zone 5b → · All zones
Zone 5a questions
How cold does it get in zone 5a?
Zone 5a is defined by an average annual extreme minimum temperature of -20 to -15°F (-28.9 to -26.1°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 5a carry some risk in a severe year.
When is the last frost in zone 5a?
It depends far more on the city than on the zone. Among 14 zone 5a cities on this site, the 30%-risk last spring frost runs from Apr 30 in Minneapolis, MN to May 16 in Casper, WY — 16 days apart (median May 4).
Which states have zone 5a?
The 2023 listings put 2,426 ZIP codes in zone 5a, spread over 19 states and territories. The most are in Iowa (563), Minnesota (270), Wisconsin (250), Vermont (176), South Dakota (168).
Did zone 5a grow on the 2023 map?
No: 2,473 ZIP codes were in zone 5a on the 2012 map and 2,426 are on the 2023 map (-47). Of today's zone 5a ZIP codes that were also listed in 2012, 44% were in a colder zone then, 55% were already 5a, and 1% were in a warmer zone. What changed in 2023.
Which big cities are in zone 5a?
The largest cities on this site in zone 5a are Minneapolis, MN, St. Paul, MN, Anchorage, AK; 14 cities in all are listed below.
How long is the growing season in zone 5a?
The median frost-free season across 14 zone 5a cities is 162 days, from 138 days in Casper to 176 days in Bloomington.