USDA Hardiness Zone 4b
Frost Dates for 55904 — Rochester, Minnesota
NOAA 1991–2020 normals from Rochester International Airport, MN (1,304 ft), 7 miles southwest.
Updated
In Rochester, the last spring frost (32°F) is around April 30 in half of years and has passed by May 13 in nine years out of ten. The first fall frost comes around October 6, as early as September 22 one year in ten, leaving a typical freeze-free season of 159 days (NOAA, Rochester International Airport, MN).
- Last spring frost
- April 30
- First fall frost
- October 6
- Growing season
- 159 days
- Hardiness zone
- 4b
50% probability
50% probability
freeze-free, 50%
-25 to -20°F (-31.7 to -28.9°C) coldest night
- First snow
- November 3
- Last snow
- April 12
- Winters with snow
- 100%
- Snow per year
- 53.1"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Rochester
Half of springs at Rochester International Airport, MN see their last 32°F night by April 30; only one in ten is past it by April 15, and one in ten still has one after May 13. Planting tender crops after May 5 leaves a 30% risk of a frost on them, after May 8 20%, and after May 13 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 October 6 in half of years, as early as September 22 one year in ten, and holds off past October 20 one year in ten. A hard freeze of 28°F follows 11 days later, around October 17; in spring the one-in-ten date for 28°F is May 2, 11 days before the 32°F one. The freeze-free season lasts 159 days in a typical year, longer than at 74% of the 142 Minnesota stations; it reaches 178 days one year in ten and falls short of 140 one year in ten. On average 156 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 9 days longer, to about May 9, and return around September 28. Severe cold of 16°F or below comes every winter, usually between November 14 and March 25.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 28 | May 2 | May 5 | May 7 | May 9 | May 12 | May 14 | May 18 | May 21 |
| 32°F | Apr 15 | Apr 21 | Apr 24 | Apr 28 | Apr 30 | May 2 | May 5 | May 8 | May 13 |
| 28°F | Apr 4 | Apr 8 | Apr 12 | Apr 15 | Apr 18 | Apr 22 | Apr 25 | Apr 29 | May 2 |
| 24°F | Mar 24 | Apr 1 | Apr 4 | Apr 6 | Apr 9 | Apr 11 | Apr 15 | Apr 19 | Apr 24 |
| 20°F | Mar 15 | Mar 21 | Mar 26 | Mar 30 | Apr 2 | Apr 4 | Apr 6 | Apr 10 | Apr 16 |
| 16°F | Mar 9 | Mar 13 | Mar 17 | Mar 20 | Mar 25 | Mar 29 | Mar 31 | Apr 3 | Apr 8 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 14 | Sep 19 | Sep 22 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 6 | Oct 11 |
| 32°F | Sep 22 | Sep 27 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 12 | Oct 16 | Oct 20 |
| 28°F | Oct 4 | Oct 8 | Oct 12 | Oct 15 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 31 |
| 24°F | Oct 13 | Oct 19 | Oct 22 | Oct 25 | Oct 28 | Oct 30 | Nov 2 | Nov 5 | Nov 11 |
| 20°F | Oct 23 | Oct 28 | Nov 1 | Nov 2 | Nov 5 | Nov 7 | Nov 11 | Nov 15 | Nov 19 |
| 16°F | Nov 1 | Nov 4 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 20 | Nov 23 | Nov 28 |
Freeze probabilities 1991–2020 at Rochester 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 55904 →Compare Rochester with another place →
Weather by month in Rochester
July is the warmest month at Rochester International Airport, MN, averaging 80°F by day and 61°F at night; January is the coldest at 23°F and 7°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 49% of years.
Warmth for growing adds up to 2,511 growing degree days a year (base 50°F), more than at 60% of the 142 Minnesota stations. 34% of them (860) have built up by the end of June, and July adds the most, 637. Precipitation totals 34.7 inches a year, most in June (5.4") and least in January (1.0"); May to September bring 63% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 23 | 7 | 1.0 | 100% | 31 | 0 |
| Feb | 27 | 11 | 1.0 | 100% | 27 | 0 |
| Mar | 40 | 23 | 2.0 | 100% | 24 | 11 |
| Apr | 55 | 35 | 3.5 | 100% | 11 | 60 |
| May | 68 | 47 | 4.4 | 49% | 1 | 262 |
| Jun | 78 | 58 | 5.4 | 0% | 0 | 527 |
| Jul | 80 | 61 | 4.2 | 0% | 0 | 637 |
| Aug | 78 | 58 | 4.1 | 0% | 0 | 563 |
| Sep | 72 | 50 | 3.6 | 27% | 1 | 345 |
| Oct | 58 | 38 | 2.4 | 100% | 9 | 96 |
| Nov | 42 | 26 | 1.8 | 100% | 23 | 10 |
| Dec | 28 | 14 | 1.3 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Rochester International Airport, MN (1,304 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Byron 4north, MN, 13 miles northwest of Rochester and 263 feet lower, has a last frost 12 days later (May 12), a first frost 8 days earlier (September 28), a season 20 days shorter.
When it snows in Rochester, Minnesota
The first measurable snow (0.1 inch or more) in Rochester usually arrives around November 3, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Rochester International Airport, MN, 6.6 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 18 days after the last snow.
Planting calendar for 55904
| When | What to do |
|---|---|
| February 19 – March 5 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 5 – March 19 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 2 – April 16 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 30 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 14 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 22 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 6 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 55904 is 7 miles from Rochester International Airport, MN, which stands at 1,304 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 55904 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°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.