USDA Hardiness Zone 3b
Frost Dates for 56649 — International Falls, Minnesota
NOAA 1991–2020 normals from International Falls International Airport, MN (1,183 ft), 2 miles southwest.
Updated
In International Falls, the last spring frost (32°F) is around May 29 in half of years and has passed by June 16 in nine years out of ten. The first fall frost comes around September 13, as early as August 30 one year in ten, leaving a typical freeze-free season of 109 days (NOAA, International Falls International Airport, MN).
- Last spring frost
- May 29
- First fall frost
- September 13
- Growing season
- 109 days
- Hardiness zone
- 3b
50% probability
50% probability
freeze-free, 50%
-35 to -30°F (-37.2 to -34.4°C) coldest night
- First snow
- October 20
- Last snow
- April 23
- Winters with snow
- 100%
- Snow per year
- 73"
median, 1991–2020
median, 1991–2020
29 of 29 observed
NOAA normal
Frost risk by date in International Falls
Half of springs at International Falls International Airport, MN see their last 32°F night by May 29; only one in ten is past it by May 13, and one in ten still has one after June 16. Planting tender crops after June 4 leaves a 30% risk of a frost on them, after June 8 20%, and after June 16 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 92% of the 142 Minnesota stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 13 in half of years, as early as August 30 one year in ten, and holds off past September 28 one year in ten. A hard freeze of 28°F follows 13 days later, around September 26; in spring the one-in-ten date for 28°F is May 30, 17 days before the 32°F one. The freeze-free season lasts 109 days in a typical year, shorter than at 99% of the 142 Minnesota stations; it reaches 128 days one year in ten and falls short of 87 one year in ten. On average 200 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between November 1 and April 13.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 13 | May 18 | May 22 | May 26 | May 29 | Jun 1 | Jun 4 | Jun 8 | Jun 16 |
| 28°F | Apr 30 | May 4 | May 7 | May 10 | May 14 | May 17 | May 21 | May 25 | May 30 |
| 24°F | Apr 20 | Apr 25 | Apr 28 | Apr 30 | May 2 | May 5 | May 8 | May 13 | May 19 |
| 20°F | Apr 9 | Apr 14 | Apr 18 | Apr 20 | Apr 23 | Apr 26 | Apr 29 | May 2 | May 8 |
| 16°F | Mar 31 | Apr 4 | Apr 7 | Apr 10 | Apr 13 | Apr 16 | Apr 18 | Apr 22 | Apr 27 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Aug 30 | Sep 3 | Sep 6 | Sep 10 | Sep 13 | Sep 17 | Sep 20 | Sep 24 | Sep 28 |
| 28°F | Sep 9 | Sep 16 | Sep 20 | Sep 23 | Sep 26 | Sep 29 | Oct 1 | Oct 5 | Oct 9 |
| 24°F | Sep 20 | Sep 26 | Sep 30 | Oct 3 | Oct 6 | Oct 9 | Oct 14 | Oct 17 | Oct 22 |
| 20°F | Oct 2 | Oct 8 | Oct 12 | Oct 16 | Oct 19 | Oct 23 | Oct 27 | Nov 1 | Nov 5 |
| 16°F | Oct 16 | Oct 21 | Oct 27 | Oct 30 | Nov 1 | Nov 4 | Nov 7 | Nov 10 | Nov 14 |
Freeze probabilities 1991–2020 at International Falls International Airport, 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 56649 →Compare International Falls with another place →
Weather by month in International Falls
July is the warmest month at International Falls International Airport, MN, averaging 78°F by day and 52°F at night; January is the coldest at 16°F and -6°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). July is the only month with under a 10% chance of a 32°F night. In spring, June still brings one in 40% of years.
Warmth for growing adds up to 1,543 growing degree days a year (base 50°F), fewer than at 97% of the 142 Minnesota stations. 31% of them (477) have built up by the end of June, and July adds the most, 460. Precipitation totals 25.4 inches a year, most in July (4.0") and least in February (0.7"); May to September bring 66% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 16 | -6 | 0.8 | 100% | 31 | 0 |
| Feb | 22 | -3 | 0.7 | 100% | 28 | 0 |
| Mar | 35 | 12 | 1.0 | 100% | 29 | 2 |
| Apr | 50 | 26 | 1.6 | 100% | 23 | 14 |
| May | 64 | 38 | 3.1 | 99% | 9 | 130 |
| Jun | 74 | 48 | 3.8 | 40% | 1 | 331 |
| Jul | 78 | 52 | 4.0 | 2% | 0 | 460 |
| Aug | 76 | 50 | 2.8 | 12% | <1 | 400 |
| Sep | 66 | 42 | 3.0 | 91% | 5 | 176 |
| Oct | 51 | 31 | 2.2 | 100% | 17 | 28 |
| Nov | 34 | 18 | 1.4 | 100% | 27 | 2 |
| Dec | 21 | 3 | 1.0 | 100% | 31 | 0 |
Monthly normals 1991–2020 at International Falls International Airport, MN (1,183 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
When it snows in International Falls, Minnesota
The first measurable snow (0.1 inch or more) in International Falls usually arrives around October 20, and the last of the season around April 23. Those are the middle dates across the winters of 1991–2020 at International Falls International Airport, MN, 1.5 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 36 days after the last snow.
Planting calendar for 56649
| When | What to do |
|---|---|
| March 20 – April 3 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 3 – April 17 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 1 – May 15 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 29 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 21 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by August 30 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 13 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 56649 is 2 miles from International Falls International Airport, MN, which stands at 1,183 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 56649 in zone 3b, the band where the coldest night of the year averaged -35 to -30°F (-37.2 to -34.4°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.