USDA Hardiness Zone 5a
Frost Dates for 50115 — Guthrie Center, Iowa
NOAA 1991–2020 normals from Guthrie Ctr, IA (1,065 ft), 2 miles southeast.
Updated
In Guthrie Center, the last spring frost (32°F) is around May 2 in half of years and has passed by May 17 in nine years out of ten. The first fall frost comes around October 3, as early as September 20 one year in ten, leaving a typical freeze-free season of 153 days (NOAA, Guthrie Ctr, IA).
- Last spring frost
- May 2
- First fall frost
- October 3
- Growing season
- 153 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 21
- Last snow
- March 18
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
26 of 26 observed
NOAA normal
Frost risk by date in Guthrie Center
Half of springs at Guthrie Ctr, IA see their last 32°F night by May 2; only one in ten is past it by April 18, and one in ten still has one after May 17. Planting tender crops after May 8 leaves a 30% risk of a frost on them, after May 11 20%, and after May 17 10%. The 15 days between the even-odds date and the one-in-ten date is wider than at 82% of the 132 Iowa stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 3 in half of years, as early as September 20 one year in ten, and holds off past October 18 one year in ten. A hard freeze of 28°F follows 12 days later, around October 15; in spring the one-in-ten date for 28°F is May 8, 9 days before the 32°F one. The freeze-free season lasts 153 days in a typical year, shorter than at 89% of the 132 Iowa stations; it reaches 172 days one year in ten and falls short of 133 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 10 days longer, to about May 12, and return around September 25. Severe cold of 16°F or below comes every winter, usually between November 11 and March 23.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 30 | May 4 | May 7 | May 9 | May 12 | May 15 | May 18 | May 22 | May 26 |
| 32°F | Apr 18 | Apr 22 | Apr 26 | Apr 30 | May 2 | May 5 | May 8 | May 11 | May 17 |
| 28°F | Apr 8 | Apr 13 | Apr 16 | Apr 19 | Apr 23 | Apr 26 | Apr 29 | May 3 | May 8 |
| 24°F | Mar 28 | Apr 2 | Apr 5 | Apr 8 | Apr 11 | Apr 14 | Apr 18 | Apr 22 | Apr 27 |
| 20°F | Mar 15 | Mar 22 | Mar 26 | Mar 30 | Apr 1 | Apr 4 | Apr 6 | Apr 10 | Apr 18 |
| 16°F | Mar 6 | Mar 12 | Mar 16 | Mar 19 | Mar 23 | Mar 27 | Mar 30 | Apr 2 | Apr 6 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 12 | Sep 16 | Sep 19 | Sep 22 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 7 |
| 32°F | Sep 20 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 10 | Oct 13 | Oct 18 |
| 28°F | Sep 30 | Oct 4 | Oct 8 | Oct 12 | Oct 15 | Oct 17 | Oct 20 | Oct 23 | Oct 28 |
| 24°F | Oct 11 | Oct 16 | Oct 20 | Oct 22 | Oct 25 | Oct 27 | Oct 30 | Nov 1 | Nov 6 |
| 20°F | Oct 21 | Oct 25 | Oct 29 | Nov 1 | Nov 2 | Nov 4 | Nov 7 | Nov 11 | Nov 16 |
| 16°F | Oct 29 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 22 | Nov 29 |
Freeze probabilities 1991–2020 at Guthrie Ctr, 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 50115 →Compare Guthrie Center with another place →
Weather by month in Guthrie Center
July is the warmest month at Guthrie Ctr, IA, averaging 85°F by day and 63°F at night; January is the coldest at 30°F and 10°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 57% of years.
Warmth for growing adds up to 3,044 growing degree days a year (base 50°F), more than at 53% of the 132 Iowa stations. 35% of them (1,072) have built up by the end of June, and July adds the most, 745.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 30 | 10 | 100% | 31 | 0 |
| Feb | 35 | 14 | 100% | 27 | 1 |
| Mar | 48 | 26 | 100% | 24 | 23 |
| Apr | 61 | 36 | 100% | 10 | 106 |
| May | 72 | 48 | 57% | 1 | 331 |
| Jun | 82 | 59 | 0% | 0 | 611 |
| Jul | 85 | 63 | 0% | 0 | 745 |
| Aug | 83 | 60 | 0% | 0 | 659 |
| Sep | 77 | 50 | 39% | 1 | 412 |
| Oct | 64 | 38 | 100% | 10 | 137 |
| Nov | 48 | 26 | 100% | 22 | 19 |
| Dec | 35 | 16 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Guthrie Ctr, IA (1,065 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, Audubon, IA, 20 miles west of Guthrie Center and 215 feet higher, has the same 50% last-frost date, the same first-frost date, a season 1 day longer.
When it snows in Guthrie Center, Iowa
The first measurable snow (0.1 inch or more) in Guthrie Center usually arrives around November 21, and the last of the season around March 18. Those are the middle dates across the winters of 1991–2020 at Guthrie Ctr, IA, 2.1 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 45 days after the last snow.
Planting calendar for 50115
| When | What to do |
|---|---|
| February 21 – March 7 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 7 – March 21 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 4 – April 18 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 2 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 11 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 19 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 3 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 50115 is 2 miles from Guthrie Ctr, IA, which stands at 1,065 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 50216 (Panora). The 2023 USDA Plant Hardiness Zone Map lists ZIP 50115 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.