USDA zone 3b in Minnesota
USDA plant hardiness zone 3b covers 38 locations across Minnesota (average annual extreme minimum −35 to −30 °F): Babbitt, MN, Baudette, MN, Bemidji, MN, Big Falls, MN, Big Falls, MN, Cook, MN, and 32 more. Average last spring frost across this group ranges May 8 (Federal Dam) to June 5 (Hibbing), and growing seasons run 93–144 days (Hibbing to Federal Dam) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Minnesota location's own frost dates; the printable planting calendar uses Rice Lake, this group's median-season location.
- USDA zone
- 3b−35 to −30 °F
- Last frost range
- May 8–Jun 5avg, 32°F
- First frost range
- Sep 8–Oct 9avg, 32°F
- Growing season range
- 93–144days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Babbitt | Hoyt Lakes | Babbitt | May 28 | Sep 14 | 108 |
| Baudette | Williams | Baudette Intl Ap | May 15 | Sep 26 | 132 |
| Bemidji | Cass Lake, Laporte | Cass Lake | May 17 | Sep 26 | 131 |
| Big Falls | — | Big Falls | May 24 | Sep 20 | 117 |
| Big Falls | Baudette, Mizpah, Kelliher | Waskish 4ne | May 22 | Sep 17 | 117 |
| Cook | — | Cook 8ne | May 12 | Oct 1 | 138 |
| Cook | — | Celina 2e | Jun 1 | Sep 15 | 104 |
| Effie | Inger, Bigfork | Marcell 5ne | May 14 | Oct 2 | 140 |
| Federal Dam | Inger, Remer, Bena | Leech Lake | May 8 | Oct 1 | 144 |
| Finland | — | Wolf Ridge Elc | May 15 | Oct 1 | 137 |
| Fosston | Gonvick, Pine Bend, McIntosh, Trail, Clearbrook, Winger, +1 more | Fosston 1 E | May 15 | Sep 26 | 132 |
| Grand Marais | — | Gunflint Lake 10 Nw | May 23 | Sep 26 | 124 |
| Greenbush | Grygla, Middle River, Strathcona, Goodridge | Goodridge 12 Nnw | May 20 | Sep 17 | 118 |
| Grygla | — | Thorhult | May 24 | Sep 20 | 120 |
| Hallock | Lake Bronson | Hallock | May 8 | Sep 30 | 142 |
| Hibbing | Nashwauk, Chisholm, Buhl, Iron Junction | Hibbing Chisholm Hibbing Ap | Jun 5 | Sep 8 | 93 |
| Hoyt Lakes | Two Harbors | Two Harbors 7nw | May 27 | Sep 23 | 117 |
| Karlstad | Newfolden, Halma, Viking, Strandquist | Argyle | May 15 | Sep 26 | 134 |
| Lancaster | Pembina, Bathgate, Humboldt | Pembina | May 16 | Sep 29 | 137 |
| Littlefork | — | Littlefork 10 Sw | May 23 | Sep 21 | 118 |
| Lutsen | — | Grand Marais | May 22 | Oct 9 | 136 |
| Lutsen | — | Lutsen 3nne | May 26 | Sep 27 | 126 |
| Meadowlands | — | Cotton | May 27 | Sep 20 | 115 |
| Meadowlands | — | Floodwood 3 Ne | May 29 | Sep 18 | 111 |
| Mountain Iron | Virginia, Biwabik, Kinney, Aurora, McKinley, Iron Junction | Eveleth Wwtp | May 12 | Oct 1 | 141 |
| Nett Lake | Orr, Littlefork | Kabetogama | May 28 | Sep 16 | 111 |
| Northome | — | Northome 3s | May 16 | Sep 26 | 131 |
| Orr | — | Orr 3e | Jun 2 | Sep 15 | 102 |
| Park Rapids | Pine Point, Nevis | Park Rapids Muni Ap | May 14 | Sep 25 | 133 |
| Plummer | Red Lake Falls, Brooks, St. Hilaire, Oklee, Erskine | Red Lake Falls | May 9 | Sep 30 | 142 |
| Ponemah | Redby, Little Rock, Red Lake, Tenstrike, Leonard | Red Lake Indian Agcy | May 12 | Oct 4 | 142 |
| Ranier | — | Intl Falls Intl Ap | May 29 | Sep 13 | 109 |
| Rice Lake * | Lake George, Pine Point, Naytahwaush, Solway, Shevlin | Itasca Univ Of Minn | May 18 | Sep 27 | 130 |
| Taconite | Deer River | Grand Rpds Forest Lab | May 17 | Sep 24 | 130 |
| Tenstrike | Blackduck, Squaw Lake | Blackduck | May 24 | Sep 17 | 115 |
| Warroad | Roseau, Badger, Roosevelt | Warroad | May 16 | Sep 24 | 129 |
| Winton | — | Ely | May 24 | Sep 23 | 121 |
| Winton | — | Ely | May 14 | Sep 29 | 135 |
* Rice Lake is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Rice Lake, representative)
Computed from Rice Lake's average frost dates — the median-season location in this Minnesotazone 3b group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Mar 23 – Apr 6 | May 25 – Jun 1 | Jul 24 – Aug 13 | — | matures comfortably |
| Pepper | Very tender | Mar 9 – Mar 23 | Jun 1 – Jun 8 | Jul 31 – Aug 30 | — | matures comfortably |
| Cucumber | Tender | Apr 20 – Apr 27 | May 25 – Jun 1 | Jul 14 – Aug 3 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 25 – Jun 1 | Jul 9 – Jul 24 | — | matures comfortably |
| Bush bean | Tender | — | May 25 – Jun 1 | Jul 14 – Jul 24 | Jul 29 – Aug 8 | matures comfortably |
| Sweet corn | Tender | — | May 18 – Jun 1 | Jul 17 – Aug 16 | — | matures comfortably |
| Basil | Very tender | Apr 6 – Apr 20 | May 25 – Jun 1 | Jun 24 – Jul 9 | — | matures comfortably |
| Lettuce | Half-hardy | Apr 6 – Apr 20 | Apr 20 – May 4 | Jun 4 – Jun 19 | Jul 15 – Jul 30 | matures comfortably |
| Pea | Hardy | — | Apr 6 – Apr 20 | May 31 – Jun 15 | Jul 5 – Jul 20 | matures comfortably |
| Spinach | Hardy | — | Apr 6 – Apr 20 | May 16 – May 26 | Jul 25 – Aug 4 | matures comfortably |
| Carrot | Half-hardy | — | Apr 27 – May 4 | Jun 26 – Jul 16 | Jun 25 – Jul 15 | matures comfortably |
| Broccoli | Half-hardy | Mar 23 – Apr 6 | Apr 20 – May 4 | Jun 14 – Jul 4 | Jun 30 – Jul 20 | matures comfortably |
Which crops fit this growing season
Using Rice Lake's own 130-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Rice Lake)
From NOAA's 1991–2020 Climate Normals at station USC00214106. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | May 29 | Jun 10 | Sep 17 | Sep 28 | 111 |
| 32°F (freeze) | May 18 | May 31 | Sep 27 | Oct 10 | 130 |
| 28°F | May 6 | May 20 | Oct 8 | Oct 22 | 153 |
| 24°F | Apr 28 | May 10 | Oct 20 | Nov 3 | 174 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 38 locations is 1,679; Rice Lake's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 1,796 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 3,446 | cool-season crops (brassicas, greens) |
Hardiness zone 3b in Minnesota
Zone 3b means an average annual extreme minimum winter temperature of about −35 to −30 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Minnesota spans 5 hardiness zones in this dataset — see all Minnesota locations for the full range, including zones3a, 4a, 4b, 5a.
Explore zone 3b in other states at zone 3b, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 3b mean in Minnesota?
- Zone 3b means an average annual extreme minimum winter temperature of −35 to −30 °F — the standard USDA measure of which perennials survive winter. 38 locations in Minnesota fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in Minnesota's zone 3b is the growing season longest?
- Federal Dam runs the longest season on this page at about 144 days; Hibbing is shortest at about 93 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in Minnesota's zone 3b?
- Using Rice Lake's frost dates (this page's median-season location): start seeds indoors about Mar 23 – Apr 6, then transplant outside about May 25 – Jun 1. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in Minnesota's zone 3b have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 38 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.