Fall in zone 4bPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 55609 (Knife River, MN)
Average last spring and first fall frost dates with 10%, 50% and 90% odds, from NOAA's 1991–2020 climate normals for the nearest weather station, Two Harbors, MN (7 miles away).
- Average last spring frostMay 1250% chance of a 32°F freeze after this date
- Average first fall frostOct 650% chance of a 32°F freeze by this date
- Growing season (frost-free)145 daysmedian, 32°F threshold
- USDA hardiness zone4b-25 to -20°F avg. coldest night
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This week in your yard
As of Oct 18, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Soil temperature now
2-inch depth
No soil station with a fresh reading within 62 miles.
4-inch depth
No soil station with a fresh reading within 62 miles.
Fall: Texas A&M AgriLife times fall pre-emergent (for winter weeds such as annual bluegrass) to soil cooling to about 70°F for several days. The 50–55°F band is the spring trigger. Always read and follow the product label.
7-day forecast and frost risk
The latest National Weather Service 7-day forecast and any Frost Advisory or Freeze Warning for 55609 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
No soil reading near this ZIP. Typical extension timing for your region: spring mid-April to early May.
Fertilizer window
Lawn region: North (cool-season). Timing only; always follow the product label.
- Kentucky bluegrass (cool-season): Early fall: Around Labor Day (late August–September); Late fall: Late October–November, before the ground freezes; Late spring: Optional around Memorial Day. Avoid: Early-spring and midsummer feeding (pushes top growth, favors crabgrass).
Plant now
No vegetable planting windows are open this week.
Prune now
No frost-timed pruning windows are open this week.
Spring-flowering shrubs are pruned right after their flowers fade, not by date. See the pruning guide.
Last spring frost odds
| Chance of a 32°F freeze after this date | Date |
|---|---|
| 90% (early: most years still freeze after this) | Apr 30 |
| 50% (the "average" last frost) | May 12 |
| 10% (cautious: only 1 year in 10 freezes later) | May 30 |
Most gardeners plant frost-tender crops (tomatoes, peppers, basil) after the 50% date, and closer to the 10% date for less risk.
First fall frost odds
| Chance the first 32°F freeze has happened by this date | Date |
|---|---|
| 10% (early: 1 year in 10 freezes this soon) | Sep 19 |
| 50% (the "average" first frost) | Oct 6 |
| 90% (late: most years have frozen by now) | Oct 21 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 28 | Sep 27 |
| 32°F (freeze) | May 12 | Oct 6 |
| 28°F (hard freeze) | Apr 29 | Oct 20 |
n/a means NOAA did not publish a date at that threshold for this station (usually because it rarely gets that cold).
Vegetable planting calendar for 55609
Dates count from your average last spring frost (May 12) and first fall frost (Oct 6). Half of years have a frost after the spring date, so give tender crops (tomatoes, peppers, squash) some slack.
| Crop | Start indoors | Spring planting | Fall planting |
|---|---|---|---|
| Tomato | Mar 17–31 | May 19–Jun 2 (transplant) | – |
| Pepper (sweet and hot) | Mar 3–17 | May 26–Jun 9 (transplant) | – |
| Eggplant | Mar 3–17 | May 26–Jun 9 (transplant) | – |
| Tomatillo | Mar 17–31 | May 19–Jun 2 (transplant) | – |
| Lettuce | Mar 17–31 | Apr 21–May 12 (transplant) Apr 14–May 26 (sow outdoors) | Aug 11–Sep 1 (transplant) Jul 28–Aug 25 (sowing) |
| Spinach | – | Mar 31–Apr 21 (sow outdoors) | Aug 11–Sep 1 (sowing) |
| Kale | Mar 17–31 | Apr 14–28 (transplant) Apr 14–28 (sow outdoors) | Jul 14–Aug 11 (transplant) Jun 30–Jul 28 (sowing) |
| Collards | Mar 17–31 | Apr 14–May 12 (transplant) Apr 14–May 12 (sow outdoors) | Jul 14–Aug 11 (transplant) Jun 30–Jul 28 (sowing) |
| Broccoli | Mar 3–17 | Apr 14–28 (transplant) | Jun 30–Jul 28 (transplant) |
| Cabbage | Mar 3–17 | Apr 14–28 (transplant) | Jun 30–Jul 28 (transplant) |
| Cauliflower | Mar 3–17 | Apr 28–May 12 (transplant) | Jun 30–Jul 28 (transplant) |
| Brussels sprouts | Feb 17–Mar 3 | Apr 14–28 (transplant) | Jun 16–Jul 7 (transplant) |
| Kohlrabi | Mar 17–31 | Apr 14–28 (transplant) Apr 14–28 (sow outdoors) | Jul 28–Aug 11 (sowing) |
| Bok choy / Asian greens | – | Apr 14–28 (sow outdoors) | Aug 11–25 (sowing) |
| Arugula | – | Apr 14–May 12 (sow outdoors) | Aug 11–Sep 8 (sowing) |
| Mustard greens | – | Apr 14–May 5 (sow outdoors) | Aug 11–25 (sowing) |
| Swiss chard | Mar 31–Apr 14 | Apr 28–May 19 (transplant) Apr 28–May 26 (sow outdoors) | Jul 28–Aug 11 (sowing) |
| Beet | – | Apr 14–May 12 (sow outdoors) | Jul 28–Aug 11 (sowing) |
| Carrot | – | Apr 21–May 19 (sow outdoors) | Jul 14–28 (sowing) |
| Radish | – | Apr 7–May 19 (sow outdoors) | Aug 25–Sep 8 (sowing) |
| Turnip | – | Apr 14–May 5 (sow outdoors) | Jul 28–Aug 11 (sowing) |
| Parsnip | – | Apr 21–May 12 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 17–Apr 14 (sow outdoors) | Jul 14–28 (sowing) |
| Onion (bulbing) | Feb 17–Mar 3 | Mar 31–Apr 14 (transplant) | – |
| Green onion / scallion | – | Mar 31–Apr 28 (sow outdoors) | Jul 28–Aug 11 (sowing) |
| Leek | Feb 17–Mar 3 | Apr 14–28 (transplant) | – |
| Garlic | – | – | Aug 25–Sep 22 (sowing) |
| Shallot | – | Mar 31–Apr 14 (transplant) | Aug 25–Sep 22 (sowing) |
| Potato | – | Apr 14–28 (transplant) | Jun 16–30 (transplant) |
| Sweet potato | – | Jun 2–16 (transplant) | – |
| Sweet corn | – | May 19–Jun 2 (sow outdoors) | – |
| Bean, bush (snap) | – | May 19–Jun 2 (sow outdoors) | – |
| Bean, pole | – | May 19–Jun 2 (sow outdoors) | – |
| Lima bean | – | May 26–Jun 9 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 2–23 (sow outdoors) | – |
| Cucumber | Apr 14–21 | May 19–Jun 2 (transplant) May 19–Jun 2 (sow outdoors) | – |
| Summer squash / zucchini | Apr 14–21 | May 19–Jun 2 (transplant) May 19–Jun 2 (sow outdoors) | – |
| Winter squash | Apr 14–21 | May 19–Jun 2 (transplant) May 19–Jun 2 (sow outdoors) | – |
| Pumpkin | – | May 19–Jun 2 (sow outdoors) | – |
| Watermelon | Apr 14–21 | May 26–Jun 9 (transplant) May 26–Jun 9 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 14–21 | May 26–Jun 9 (transplant) May 26–Jun 9 (sow outdoors) | – |
| Okra | Mar 31–Apr 14 | May 26–Jun 9 (transplant) May 26–Jun 9 (sow outdoors) | – |
| Celery | Feb 17–Mar 3 | May 19–26 (transplant) | – |
| Basil | Mar 31–Apr 14 | May 19–Jun 2 (transplant) May 19–Jun 2 (sow outdoors) | – |
| Cilantro | – | Apr 28–May 26 (sow outdoors) | Aug 11–25 (sowing) |
| Parsley | Mar 3–17 | Apr 28–May 12 (transplant) Apr 21–May 12 (sow outdoors) | – |
| Dill | – | May 12–26 (sow outdoors) | Aug 11–25 (sowing) |
| Sunflower | – | May 12–26 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 14–28 (transplant) | – |
| Rhubarb (crowns) | – | Apr 14–28 (transplant) | – |
| Strawberry (plants) | – | Apr 14–28 (transplant) | Jul 28–Aug 25 (transplant) |
Typical ranges from university extension planting calendars, adjusted to your frost dates. Probabilities, not guarantees. Fall windows that would overlap spring planting are left out, as are fall crops of frost-tender plants where the frost-free season is under 210 days.
Where these numbers come from
Station: Two Harbors, MN (NOAA GHCN-Daily ID USC00218419), elevation 625 ft, 7.1 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Two Harbors 7NW, MN | 12 mi | May 27 | Sep 23 |
| Island Lake 4E, MN | 14 mi | May 21 | Sep 27 |
| Duluth Harbor STN, MN | 20 mi | May 14 | Oct 12 |
The average last-frost dates of these stations span 15 days, a rough guide to local variation. See data sources & methods.
Frost questions for 55609
When is the last frost in 55609?
The average (50% chance) last spring freeze of 32°F for ZIP 55609 is May 12. For a more cautious planting date, use May 30, when only 1 year in 10 still sees a later freeze.
When is the first frost in 55609?
The average first fall freeze is October 6. In 1 year in 10 it comes by September 19.
What hardiness zone is 55609?
ZIP 55609 is in USDA zone 4b (-25 to -20°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 55609 right now?
This page shows the latest 2-inch and 4-inch soil temperature from the nearest public soil station (USDA SCAN, NOAA USCRN or TexMesonet), or a labeled estimate when no station is close, against the 50–55°F spring pre-emergent band.
Nearby ZIP codes
55804 Duluth 55803 Rice Lake 55812 Duluth 55805 Duluth 55802 Duluth 55616 Two Harbors 55806 Duluth 55814 Hermantown
Other ZIP codes in Lake County
55601 55603 55607 55614 55616 55731 55796 All Lake County frost dates · Minnesota frost dates
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- Freeze alerts
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Free. One weekly email plus alerts when your ZIP has a frost or a soil-temperature change worth acting on. After you submit, Kit (our email provider) sends a confirmation email: check your email and click the link to confirm. You aren't subscribed until you do. We collect only your email address and ZIP, sent to Kit to deliver The Dial. Unsubscribe anytime.