USDA Hardiness Zone 5a
Frost Dates for 55120 — Mendota Heights, Minnesota
NOAA 1991–2020 normals from St Paul 3SW, MN (925 ft), 4 miles north.
Updated
In Mendota Heights, the last spring frost (32°F) is around April 25 in half of years and has passed by May 9 in nine years out of ten. The first fall frost comes around October 12, as early as October 1 one year in ten, leaving a typical freeze-free season of 169 days (NOAA, St Paul 3SW, MN).
- Last spring frost
- April 25
- First fall frost
- October 12
- Growing season
- 169 days
- Hardiness zone
- 5a
50% probability
50% probability
freeze-free, 50%
-20 to -15°F (-28.9 to -26.1°C) coldest night
- First snow
- November 9
- Last snow
- April 12
- Winters with snow
- 100%
- Snow per year
- 51.2"
median, 1991–2020
median, 1991–2020
26 of 26 observed
NOAA normal
Frost risk by date in Mendota Heights
Half of springs at St Paul 3SW, MN see their last 32°F night by April 25; only one in ten is past it by April 9, and one in ten still has one after May 9. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 3 20%, and after May 9 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 37% of the 142 Minnesota stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 12 in half of years, as early as October 1 one year in ten, and holds off past October 25 one year in ten. A hard freeze of 28°F follows 11 days later, around October 23; in spring the one-in-ten date for 28°F is April 27, 12 days before the 32°F one. The freeze-free season lasts 169 days in a typical year, longer than at 91% of the 142 Minnesota stations; it reaches 188 days one year in ten and falls short of 149 one year in ten. On average 147 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 May 6, and return around October 3. Severe cold of 16°F or below comes every winter, usually between November 18 and March 21.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 21 | Apr 27 | May 1 | May 3 | May 6 | May 9 | May 12 | May 16 | May 22 |
| 32°F | Apr 9 | Apr 14 | Apr 19 | Apr 21 | Apr 25 | Apr 28 | May 1 | May 3 | May 9 |
| 28°F | Apr 1 | Apr 4 | Apr 7 | Apr 10 | Apr 12 | Apr 16 | Apr 19 | Apr 22 | Apr 27 |
| 24°F | Mar 21 | Mar 27 | Mar 31 | Apr 2 | Apr 4 | Apr 6 | Apr 9 | Apr 13 | Apr 19 |
| 20°F | Mar 13 | Mar 18 | Mar 21 | Mar 25 | Mar 29 | Mar 31 | Apr 3 | Apr 5 | Apr 10 |
| 16°F | Mar 6 | Mar 11 | Mar 15 | Mar 18 | Mar 21 | Mar 24 | Mar 28 | Mar 31 | Apr 4 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 22 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 11 | Oct 14 |
| 32°F | Oct 1 | Oct 4 | Oct 7 | Oct 9 | Oct 12 | Oct 15 | Oct 17 | Oct 20 | Oct 25 |
| 28°F | Oct 10 | Oct 14 | Oct 18 | Oct 20 | Oct 23 | Oct 25 | Oct 28 | Nov 1 | Nov 5 |
| 24°F | Oct 19 | Oct 23 | Oct 27 | Oct 30 | Nov 2 | Nov 4 | Nov 7 | Nov 10 | Nov 14 |
| 20°F | Oct 30 | Nov 2 | Nov 5 | Nov 8 | Nov 10 | Nov 13 | Nov 16 | Nov 19 | Nov 25 |
| 16°F | Nov 5 | Nov 9 | Nov 12 | Nov 16 | Nov 18 | Nov 21 | Nov 24 | Nov 28 | Dec 3 |
Freeze probabilities 1991–2020 at St Paul 3SW, 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 55120 →Compare Mendota Heights with another place →
Weather by month in Mendota Heights
July is the warmest month at St Paul 3SW, MN, averaging 82°F by day and 64°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 September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 30% of years.
Warmth for growing adds up to 2,709 growing degree days a year (base 50°F), more than at 83% of the 142 Minnesota stations. 33% of them (906) have built up by the end of June, and July adds the most, 711.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 23 | 7 | 100% | 31 | 0 |
| Feb | 28 | 12 | 100% | 28 | 0 |
| Mar | 41 | 23 | 100% | 23 | 14 |
| Apr | 55 | 37 | 98% | 10 | 73 |
| May | 68 | 48 | 30% | 1 | 275 |
| Jun | 77 | 59 | 0% | 0 | 544 |
| Jul | 82 | 64 | 0% | 0 | 711 |
| Aug | 79 | 62 | 0% | 0 | 636 |
| Sep | 72 | 52 | 9% | 0 | 364 |
| Oct | 58 | 38 | 97% | 6 | 89 |
| Nov | 41 | 26 | 100% | 20 | 4 |
| Dec | 28 | 14 | 100% | 30 | 0 |
Monthly normals 1991–2020 at St Paul 3SW, MN (925 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, Minneapolis/St Paul Airport, MN, 4 miles west of Mendota Heights, has a last frost 2 days earlier (April 23), a first frost 6 days later (October 18), a season 7 days longer.
When it snows in Mendota Heights, Minnesota
The first measurable snow (0.1 inch or more) in Mendota Heights usually arrives around November 9, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Minneapolis/St Paul Airport, MN, 4.1 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 13 days after the last snow.
Planting calendar for 55120
| When | What to do |
|---|---|
| February 14 – February 28 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 28 – March 14 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 28 – April 11 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 25 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 20 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 28 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 12 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 55120 is 4 miles from St Paul 3SW, MN, which stands at 925 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 55104 (Saint Paul). The 2023 USDA Plant Hardiness Zone Map lists ZIP 55120 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°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.