USDA Hardiness Zone 5b
Frost Dates for 50013 — ZIP 50013
NOAA 1991–2020 normals from Ames Municipal Airport, IA (930 ft), 2 miles southeast.
Updated
In ZIP 50013, the last spring frost (32°F) is around April 26 in half of years and has passed by May 9 in nine years out of ten. The first fall frost comes around October 8, as early as September 23 one year in ten, leaving a typical freeze-free season of 164 days (NOAA, Ames Municipal Airport, IA).
- Last spring frost
- April 26
- First fall frost
- October 8
- Growing season
- 164 days
- Hardiness zone
- 5b
50% probability
50% probability
freeze-free, 50%
-15 to -10°F (-26.1 to -23.3°C) coldest night
- First snow
- November 24
- Last snow
- March 20
- Winters with snow
- 100%
- Snow per year
- 27.3"
median, 1991–2020
median, 1991–2020
28 of 28 observed
NOAA normal
Frost risk by date in ZIP 50013
Half of springs at Ames Municipal Airport, IA see their last 32°F night by April 26; only one in ten is past it by April 11, and one in ten still has one after May 9. Planting tender crops after May 2 leaves a 30% risk of a frost on them, after May 5 20%, and after May 9 10%. The 13 days between the even-odds date and the one-in-ten date measure how much the end of the frost season moves from year to year.
In fall the first 32°F night comes by October 8 in half of years, as early as September 23 one year in ten, and holds off past October 21 one year in ten. A hard freeze of 28°F follows 11 days later, around October 19; in spring the one-in-ten date for 28°F is May 1, 8 days before the 32°F one. The freeze-free season lasts 164 days in a typical year; it reaches 184 days one year in ten and falls short of 144 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 9 days longer, to about May 5, and return around September 28. Severe cold of 16°F or below comes every winter, usually between November 15 and March 15.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 21 | Apr 27 | May 1 | May 3 | May 5 | May 7 | May 10 | May 13 | May 17 |
| 32°F | Apr 11 | Apr 15 | Apr 19 | Apr 22 | Apr 26 | Apr 29 | May 2 | May 5 | May 9 |
| 28°F | Apr 1 | Apr 5 | Apr 8 | Apr 11 | Apr 14 | Apr 17 | Apr 21 | Apr 25 | May 1 |
| 24°F | Mar 17 | Mar 25 | Mar 30 | Apr 2 | Apr 4 | Apr 7 | Apr 10 | Apr 15 | Apr 21 |
| 20°F | Mar 7 | Mar 13 | Mar 17 | Mar 21 | Mar 26 | Mar 30 | Apr 2 | Apr 6 | Apr 13 |
| 16°F | Mar 1 | Mar 5 | Mar 8 | Mar 11 | Mar 15 | Mar 18 | Mar 22 | Mar 28 | Apr 2 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 15 | Sep 19 | Sep 22 | Sep 26 | Sep 28 | Oct 1 | Oct 4 | Oct 7 | Oct 11 |
| 32°F | Sep 23 | Sep 28 | Oct 2 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 17 | Oct 21 |
| 28°F | Oct 4 | Oct 10 | Oct 14 | Oct 16 | Oct 19 | Oct 21 | Oct 23 | Oct 26 | Oct 31 |
| 24°F | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Oct 31 | Nov 2 | Nov 5 | Nov 10 |
| 20°F | Oct 24 | Oct 30 | Nov 1 | Nov 4 | Nov 6 | Nov 8 | Nov 12 | Nov 16 | Nov 21 |
| 16°F | Nov 2 | Nov 6 | Nov 9 | Nov 12 | Nov 15 | Nov 19 | Nov 23 | Nov 27 | Dec 2 |
Freeze probabilities 1991–2020 at Ames Municipal Airport, 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 50013 →Compare ZIP 50013 with another place →
Weather by month in ZIP 50013
July is the warmest month at Ames Municipal Airport, IA, averaging 84°F by day and 63°F at night; January is the coldest at 29°F and 11°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 35% of years.
Warmth for growing adds up to 3,021 growing degree days a year (base 50°F). 36% of them (1,088) have built up by the end of June, and July adds the most, 724. Precipitation totals 36.1 inches a year, most in May (5.2") and least in January (0.6"); May to September bring 64% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 29 | 11 | 0.6 | 100% | 30 | 0 |
| Feb | 33 | 15 | 0.8 | 100% | 27 | 1 |
| Mar | 47 | 27 | 2.0 | 100% | 23 | 25 |
| Apr | 61 | 38 | 3.9 | 99% | 8 | 105 |
| May | 72 | 50 | 5.2 | 35% | 1 | 342 |
| Jun | 81 | 60 | 5.2 | 0% | 0 | 616 |
| Jul | 84 | 63 | 4.4 | 0% | 0 | 724 |
| Aug | 82 | 60 | 4.9 | 0% | 0 | 649 |
| Sep | 76 | 51 | 3.3 | 26% | <1 | 407 |
| Oct | 63 | 39 | 2.8 | 99% | 8 | 136 |
| Nov | 47 | 27 | 1.9 | 100% | 21 | 16 |
| Dec | 34 | 17 | 1.1 | 100% | 29 | 1 |
Monthly normals 1991–2020 at Ames Municipal Airport, IA (930 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, Ames 5 SE, IA, 6 miles southeast of ZIP 50013, has the same 50% last-frost date, a first frost 4 days later (October 12), a season 4 days longer.
When it snows in ZIP 50013
The first measurable snow (0.1 inch or more) in ZIP 50013 usually arrives around November 24, and the last of the season around March 20. Those are the middle dates across the winters of 1991–2020 at Ames 5 SE, IA, 6.3 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 37 days after the last snow.
Planting calendar for 50013
| When | What to do |
|---|---|
| February 15 – March 1 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 1 – March 15 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 29 – April 12 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 26 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 16 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 24 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 8 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 50013 is 2 miles from Ames Municipal Airport, IA, which stands at 930 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 50010 (Ames). The 2023 USDA Plant Hardiness Zone Map lists ZIP 50013 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°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.