USDA Hardiness Zone 4a
Frost Dates for 55803 — Duluth, Minnesota
NOAA 1991–2020 normals from Island Lake 4E, MN (1,410 ft), 4 miles north.
Updated
In Duluth, the last spring frost (32°F) is around May 21 in half of years and has passed by June 3 in nine years out of ten. The first fall frost comes around September 27, as early as September 13 one year in ten, leaving a typical freeze-free season of 129 days (NOAA, Island Lake 4E, MN).
- Last spring frost
- May 21
- First fall frost
- September 27
- Growing season
- 129 days
- Hardiness zone
- 4a
50% probability
50% probability
freeze-free, 50%
-30 to -25°F (-34.4 to -31.7°C) coldest night
- First snow
- October 25
- Last snow
- April 27
- Winters with snow
- 100%
- Snow per year
- 90.2"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Duluth
Half of springs at Island Lake 4E, MN see their last 32°F night by May 21; only one in ten is past it by May 6, and one in ten still has one after June 3. Planting tender crops after May 27 leaves a 30% risk of a frost on them, after May 30 20%, and after June 3 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 61% of the 142 Minnesota stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 27 in half of years, as early as September 13 one year in ten, and holds off past October 10 one year in ten. A hard freeze of 28°F follows 10 days later, around October 7; in spring the one-in-ten date for 28°F is May 23, 11 days before the 32°F one. The freeze-free season lasts 129 days in a typical year, shorter than at 94% of the 142 Minnesota stations; it reaches 148 days one year in ten and falls short of 110 one year in ten. On average 190 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 11 days longer, to about June 1, and return around September 17. Severe cold of 16°F or below comes every winter, usually between November 8 and April 8.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 20 | May 24 | May 27 | May 30 | Jun 1 | Jun 3 | Jun 6 | Jun 10 | Jun 17 |
| 32°F | May 6 | May 11 | May 15 | May 18 | May 21 | May 24 | May 27 | May 30 | Jun 3 |
| 28°F | Apr 25 | Apr 29 | May 1 | May 4 | May 7 | May 10 | May 15 | May 18 | May 23 |
| 24°F | Apr 13 | Apr 18 | Apr 22 | Apr 24 | Apr 27 | Apr 30 | May 2 | May 6 | May 13 |
| 20°F | Apr 4 | Apr 8 | Apr 10 | Apr 13 | Apr 16 | Apr 19 | Apr 22 | Apr 26 | Apr 30 |
| 16°F | Mar 29 | Apr 2 | Apr 4 | Apr 6 | Apr 8 | Apr 10 | Apr 13 | Apr 17 | Apr 22 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 3 | Sep 8 | Sep 12 | Sep 14 | Sep 17 | Sep 19 | Sep 22 | Sep 26 | Sep 30 |
| 32°F | Sep 13 | Sep 18 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 10 |
| 28°F | Sep 25 | Sep 29 | Oct 2 | Oct 5 | Oct 7 | Oct 10 | Oct 13 | Oct 17 | Oct 22 |
| 24°F | Oct 5 | Oct 9 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 26 | Oct 30 | Nov 3 |
| 20°F | Oct 14 | Oct 20 | Oct 25 | Oct 29 | Oct 31 | Nov 3 | Nov 5 | Nov 8 | Nov 13 |
| 16°F | Oct 28 | Nov 1 | Nov 3 | Nov 6 | Nov 8 | Nov 10 | Nov 14 | Nov 17 | Nov 21 |
Freeze probabilities 1991–2020 at Island Lake 4E, MN, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 55803 →Compare Duluth with another place →
Compared with the next station
The nearest other station, Duluth, MN, 11 miles southwest of Duluth, has a last frost 8 days earlier (May 13), a first frost 4 days later (October 1), a season 11 days longer.
When it snows in Duluth, Minnesota
The first measurable snow (0.1 inch or more) in Duluth usually arrives around October 25, and the last of the season around April 27. Those are the middle dates across the winters of 1991–2020 at Duluth, MN, 10.7 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 24 days after the last snow.
Planting calendar for 55803
| When | What to do |
|---|---|
| March 12 – March 26 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 26 – April 9 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 23 – May 7 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 21 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 5 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 13 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 27 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 55803 is 4 miles from Island Lake 4E, MN, which stands at 1,410 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 55803 in zone 4a, the band where the coldest night of the year averaged -30 to -25°F (-34.4 to -31.7°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Minnesota →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.