USDA Hardiness Zone 5a
Frost Dates for 50588 — Storm Lake, Iowa
NOAA 1991–2020 normals from Storm Lake, IA (1,442 ft), under a mile west.
Updated
In Storm Lake, the last spring frost (32°F) is around April 25 in half of years and has passed by May 7 in nine years out of ten. The first fall frost comes around October 13, as early as October 1 one year in ten, leaving a typical freeze-free season of 170 days (NOAA, Storm Lake, IA).
- Last spring frost
- April 25
- First fall frost
- October 13
- Growing season
- 170 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 18
- Last snow
- March 28
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
28 of 28 observed
NOAA normal
Frost risk by date in Storm Lake
Half of springs at Storm Lake, IA see their last 32°F night by April 25; only one in ten is past it by April 11, and one in ten still has one after May 7. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 3 20%, and after May 7 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 67% of the 132 Iowa stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 13 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 10 days later, around October 23; in spring the one-in-ten date for 28°F is April 29, 8 days before the 32°F one. The freeze-free season lasts 170 days in a typical year, longer than at 69% of the 132 Iowa stations; it reaches 189 days one year in ten and falls short of 151 one year in ten. On average 151 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 4, and return around October 3. Severe cold of 16°F or below comes every winter, usually between November 16 and March 20.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 22 | Apr 27 | Apr 30 | May 2 | May 4 | May 6 | May 8 | May 11 | May 16 |
| 32°F | Apr 11 | Apr 16 | Apr 19 | Apr 22 | Apr 25 | Apr 29 | May 1 | May 3 | May 7 |
| 28°F | Apr 2 | Apr 6 | Apr 9 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 29 |
| 24°F | Mar 22 | Mar 28 | Apr 1 | Apr 3 | Apr 6 | Apr 9 | Apr 11 | Apr 15 | Apr 20 |
| 20°F | Mar 13 | Mar 18 | Mar 22 | Mar 26 | Mar 31 | Apr 1 | Apr 4 | Apr 8 | Apr 13 |
| 16°F | Mar 6 | Mar 10 | Mar 14 | Mar 17 | Mar 20 | Mar 24 | Mar 28 | Apr 1 | Apr 6 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 21 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 11 | Oct 15 |
| 32°F | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 18 | Oct 21 | Oct 25 |
| 28°F | Oct 11 | Oct 15 | Oct 18 | Oct 21 | Oct 23 | Oct 26 | Oct 28 | Nov 1 | Nov 5 |
| 24°F | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 10 | Nov 16 |
| 20°F | Oct 27 | Nov 1 | Nov 3 | Nov 6 | Nov 8 | Nov 11 | Nov 15 | Nov 19 | Nov 27 |
| 16°F | Nov 2 | Nov 6 | Nov 10 | Nov 13 | Nov 16 | Nov 20 | Nov 24 | Nov 29 | Dec 5 |
Freeze probabilities 1991–2020 at Storm Lake, IA, 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 50588 →Compare Storm Lake with another place →
Weather by month in Storm Lake
July is the warmest month at Storm Lake, IA, averaging 82°F by day and 64°F at night; January is the coldest at 26°F and 9°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 32% of years.
Warmth for growing adds up to 2,908 growing degree days a year (base 50°F), fewer than at 61% of the 132 Iowa stations. 35% of them (1,006) have built up by the end of June, and July adds the most, 713.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 26 | 9 | 100% | 31 | 0 |
| Feb | 30 | 13 | 100% | 27 | 0 |
| Mar | 43 | 25 | 100% | 24 | 16 |
| Apr | 58 | 37 | 100% | 10 | 90 |
| May | 69 | 49 | 32% | 1 | 308 |
| Jun | 79 | 60 | 0% | 0 | 591 |
| Jul | 82 | 64 | 0% | 0 | 713 |
| Aug | 80 | 61 | 0% | 0 | 640 |
| Sep | 74 | 53 | 10% | <1 | 408 |
| Oct | 61 | 40 | 97% | 8 | 127 |
| Nov | 44 | 27 | 100% | 22 | 14 |
| Dec | 31 | 15 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Storm Lake, IA (1,442 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, Sac City, IA, 19 miles southeast of Storm Lake and 232 feet lower, has a last frost 5 days later (April 30), a first frost 7 days earlier (October 6), a season 12 days shorter.
When it snows in Storm Lake, Iowa
The first measurable snow (0.1 inch or more) in Storm Lake usually arrives around November 18, and the last of the season around March 28. Those are the middle dates across the winters of 1991–2020 at Storm Lake, IA, 0.6 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 28 days after the last snow.
Planting calendar for 50588
| 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 21 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 29 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 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 50588 is under a mile from Storm Lake, IA, which stands at 1,442 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 50588 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.
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.