Oslo, MN frost dates
Last spring frostMay 5median date
First fall frostOct 2median date
Growing season150 daysfrost-free
Hardiness zone4aZone 4a
How Oslo compares
- In 8 years out of 10, the last spring frost in Oslo falls between April 24 and May 22, a 28-day window. The first fall frost falls between September 20 and October 13.
- The median last frost is the same as the Minnesota median of May 5.
- Its 150-day growing season is longer than 42% of the 801 Minnesota places with a regular frost season (state median 151 days).
- The last frost is 7 days earlier than the zone 4a median of May 12. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4a chart.
- The weather station records an average of 184 nights a year at or below 32°F.
- Compared with Grand Forks, ND, 32 km away, the last frost here is 5 days earlier than there and the growing season is 6 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 24 |
| 50% (median) | May 5 |
| 10% (safe for tender plants) | May 22 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 20 |
| 50% (median) | October 2 |
| 90% (late) | October 13 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Oslo, MN
Oslo, MN frost dates — last frost May 5, first frost Oct 2, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Feb 10 to Feb 24Transplant outside: Apr 7 to Apr 21
Start indoors: Feb 24 to Mar 10Transplant outside: May 19 to Jun 2
Start indoors: Feb 24 to Mar 10Transplant outside: May 19 to Jun 2
Start indoors: Mar 10 to Mar 24Transplant outside: May 12 to May 26
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 14 to Apr 28Sow outdoors: Apr 7 to May 12Plant for fall: Aug 7 to Sep 4
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 7 to Apr 21Sow outdoors: Apr 7 to Apr 21Plant for fall: Jul 24 to Aug 14
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 21 to May 5Plant for fall: Jun 26 to Jul 17
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 14 to Apr 28Plant for fall: Jun 26 to Jul 17
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 21 to May 5Plant for fall: Jun 26 to Jul 17
Start indoors: Mar 24 to Apr 7Transplant outside: May 26 to Jun 9Sow outdoors: May 26 to Jun 9
Start indoors: Mar 24 to Apr 7Transplant outside: May 12 to May 26
Sow outdoors: Mar 24 to Apr 14Plant for fall: Jul 10 to Jul 31
Sow outdoors: Mar 24 to Apr 14Plant for fall: Aug 7 to Aug 28
Sow outdoors: Mar 31 to May 12Plant for fall: Aug 21 to Sep 11
Start indoors: Apr 7 to Apr 14Transplant outside: May 19 to May 26Sow outdoors: May 12 to May 26Plant for fall: Jul 17 to Jul 31
Start indoors: Apr 7 to Apr 14Sow outdoors: May 12 to May 26Plant for fall: Jul 24 to Aug 7
Start indoors: Apr 7 to Apr 14Sow outdoors: May 12 to May 26
Start indoors: Apr 7 to Apr 14Transplant outside: May 19 to Jun 2
Sow outdoors: Apr 14 to May 12Plant for fall: Jul 10 to Jul 24
Sow outdoors: Apr 14 to May 12Plant for fall: Jul 24 to Aug 7
Sow outdoors: Apr 14 to May 5
Sow outdoors: Apr 21 to May 19Plant for fall: Jul 24 to Aug 7
Sow outdoors: Apr 21 to May 12Plant for fall: Aug 7 to Aug 28
Sow outdoors: May 12 to Jun 2Plant for fall: Jul 17 to Jul 31
Sow outdoors: May 12 to May 26
Transplant outside: May 19 to Jun 9
Plant for fall: Sep 18 to Oct 23
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Oslo, MN
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 10 – Feb 24 | Apr 7 – Apr 21 | — | — |
| Peppers | Feb 24 – Mar 10 | May 19 – Jun 2 | — | — |
| Eggplant | Feb 24 – Mar 10 | May 19 – Jun 2 | — | — |
| Tomatoes | Mar 10 – Mar 24 | May 12 – May 26 | — | — |
| Lettuce | Mar 10 – Mar 24 | Apr 14 – Apr 28 | Apr 7 – May 12 | Aug 7 – Sep 4 |
| Kale | Mar 10 – Mar 24 | Apr 7 – Apr 21 | Apr 7 – Apr 21 | Jul 24 – Aug 14 |
| Broccoli | Mar 10 – Mar 24 | Apr 21 – May 5 | — | Jun 26 – Jul 17 |
| Cabbage | Mar 10 – Mar 24 | Apr 14 – Apr 28 | — | Jun 26 – Jul 17 |
| Cauliflower | Mar 10 – Mar 24 | Apr 21 – May 5 | — | Jun 26 – Jul 17 |
| Okra | Mar 24 – Apr 7 | May 26 – Jun 9 | May 26 – Jun 9 | — |
| Basil | Mar 24 – Apr 7 | May 12 – May 26 | — | — |
| Peas | — | — | Mar 24 – Apr 14 | Jul 10 – Jul 31 |
| Spinach | — | — | Mar 24 – Apr 14 | Aug 7 – Aug 28 |
| Radishes | — | — | Mar 31 – May 12 | Aug 21 – Sep 11 |
| Cucumbers | Apr 7 – Apr 14 | May 19 – May 26 | May 12 – May 26 | Jul 17 – Jul 31 |
| Zucchini & Summer Squash | Apr 7 – Apr 14 | — | May 12 – May 26 | Jul 24 – Aug 7 |
| Winter Squash & Pumpkins | Apr 7 – Apr 14 | — | May 12 – May 26 | — |
| Melons & Watermelon | Apr 7 – Apr 14 | May 19 – Jun 2 | — | — |
| Carrots | — | — | Apr 14 – May 12 | Jul 10 – Jul 24 |
| Beets | — | — | Apr 14 – May 12 | Jul 24 – Aug 7 |
| Potatoes | — | — | Apr 14 – May 5 | — |
| Swiss Chard | — | — | Apr 21 – May 19 | Jul 24 – Aug 7 |
| Cilantro | — | — | Apr 21 – May 12 | Aug 7 – Aug 28 |
| Green Beans | — | — | May 12 – Jun 2 | Jul 17 – Jul 31 |
| Sweet Corn | — | — | May 12 – May 26 | — |
| Sweet Potatoes | — | May 19 – Jun 9 | — | — |
| Garlic | — | — | — | Sep 18 – Oct 23 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Warren Wsd, MN weather station, 25 km away (elevation 856 ft (261 m)).
Frost dates near Oslo
- Alvarado May 5 · Oct 2
- Argyle May 15 · Sep 26
- Warren May 5 · Oct 2
- East Grand Forks May 10 · Oct 1
- Stephen May 15 · Sep 26
- Euclid May 11 · Sep 27
- Donaldson May 8 · Sep 30
- Viking May 5 · Oct 2
- Kennedy May 8 · Sep 30
- Fisher May 11 · Sep 27
Frequently asked questions
When is the last frost in Oslo, MN?
The median last spring frost in Oslo, MN is May 5. There is still about a 10% chance of frost after May 22, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Oslo, MN?
The median first fall frost is October 2, with about a 10% chance of frost before September 20.
How long is the growing season in Oslo, MN?
About 150 days between the median last spring frost and first fall frost.
What planting zone is Oslo, MN?
Oslo, MN is in USDA hardiness zone 4a.