USDA Hardiness Zone 6a
Frost Dates for 47993 — Williamsport, Indiana
NOAA 1991–2020 normals from Attica 2E, IN (727 ft), 10 miles east.
Updated
In Williamsport, the last spring frost (32°F) is around April 22 in half of years and has passed by May 8 in nine years out of ten. The first fall frost comes around October 17, as early as October 1 one year in ten, leaving a typical freeze-free season of 176 days (NOAA, Attica 2E, IN).
- Last spring frost
- April 22
- First fall frost
- October 17
- Growing season
- 176 days
- Hardiness zone
- 6a
50% probability
50% probability
freeze-free, 50%
-10 to -5°F (-23.3 to -20.6°C) coldest night
- First snow
- November 29
- Last snow
- March 17
- Winters with snow
- 100%
- Snow per year
- 23.3"
median, 1991–2020
median, 1991–2020
20 of 20 observed
NOAA normal
Frost risk by date in Williamsport
Half of springs at Attica 2E, IN see their last 32°F night by April 22; only one in ten is past it by April 8, and one in ten still has one after May 8. Planting tender crops after April 29 leaves a 30% risk of a frost on them, after May 2 20%, and after May 8 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 35% of the 125 Indiana stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 17 in half of years, as early as October 1 one year in ten, and holds off past October 30 one year in ten. A hard freeze of 28°F follows 11 days later, around October 28; in spring the one-in-ten date for 28°F is April 27, 11 days before the 32°F one. The freeze-free season lasts 176 days in a typical year, shorter than at 67% of the 125 Indiana stations; it reaches 193 days one year in ten and falls short of 156 one year in ten. On average 129 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 3, and return around October 6. Severe cold of 16°F or below comes every winter, usually between November 27 and March 12.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 19 | Apr 23 | Apr 27 | Apr 30 | May 3 | May 6 | May 9 | May 14 | May 20 |
| 32°F | Apr 8 | Apr 13 | Apr 17 | Apr 20 | Apr 22 | Apr 26 | Apr 29 | May 2 | May 8 |
| 28°F | Mar 30 | Apr 3 | Apr 6 | Apr 8 | Apr 11 | Apr 14 | Apr 18 | Apr 22 | Apr 27 |
| 24°F | Mar 14 | Mar 20 | Mar 26 | Mar 30 | Apr 1 | Apr 3 | Apr 6 | Apr 10 | Apr 17 |
| 20°F | Mar 4 | Mar 10 | Mar 14 | Mar 17 | Mar 22 | Mar 25 | Mar 29 | Apr 1 | Apr 5 |
| 16°F | Feb 21 | Feb 28 | Mar 4 | Mar 8 | Mar 12 | Mar 15 | Mar 18 | Mar 23 | Mar 30 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 23 | Sep 28 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 19 |
| 32°F | Oct 1 | Oct 8 | Oct 12 | Oct 15 | Oct 17 | Oct 20 | Oct 22 | Oct 25 | Oct 30 |
| 28°F | Oct 15 | Oct 19 | Oct 22 | Oct 25 | Oct 28 | Oct 30 | Nov 1 | Nov 5 | Nov 10 |
| 24°F | Oct 25 | Oct 30 | Nov 1 | Nov 4 | Nov 7 | Nov 10 | Nov 14 | Nov 17 | Nov 23 |
| 20°F | Nov 3 | Nov 7 | Nov 11 | Nov 15 | Nov 18 | Nov 21 | Nov 24 | Nov 28 | Dec 3 |
| 16°F | Nov 10 | Nov 16 | Nov 21 | Nov 24 | Nov 27 | Nov 30 | Dec 4 | Dec 9 | Dec 17 |
Freeze probabilities 1991–2020 at Attica 2E, IN, 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 47993 →Compare Williamsport with another place →
Weather by month in Williamsport
July is the warmest month at Attica 2E, IN, averaging 84°F by day and 62°F at night; January is the coldest at 33°F and 16°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 25% of years.
Warmth for growing adds up to 3,249 growing degree days a year (base 50°F), fewer than at 58% of the 125 Indiana stations. 36% of them (1,180) have built up by the end of June, and July adds the most, 715. Precipitation totals 40.0 inches a year, most in June (4.9") and least in February (1.9"); May to September bring 50% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 33 | 16 | 2.3 | 100% | 28 | 2 |
| Feb | 38 | 19 | 1.9 | 100% | 25 | 3 |
| Mar | 49 | 28 | 2.9 | 100% | 21 | 31 |
| Apr | 62 | 39 | 4.1 | 98% | 7 | 134 |
| May | 73 | 51 | 4.2 | 25% | <1 | 379 |
| Jun | 82 | 60 | 4.9 | 0% | 0 | 631 |
| Jul | 84 | 62 | 4.8 | 0% | 0 | 715 |
| Aug | 83 | 60 | 3.5 | 0% | 0 | 665 |
| Sep | 78 | 53 | 2.7 | 9% | <1 | 471 |
| Oct | 66 | 42 | 3.2 | 92% | 5 | 181 |
| Nov | 50 | 31 | 3.1 | 100% | 17 | 33 |
| Dec | 38 | 22 | 2.4 | 100% | 26 | 5 |
Monthly normals 1991–2020 at Attica 2E, IN (727 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, Boswell 4WNW, IN, 17 miles north of Williamsport, has a last frost 3 days later (April 25), a first frost 4 days earlier (October 13), a season 7 days shorter.
When it snows in Williamsport, Indiana
The first measurable snow (0.1 inch or more) in Williamsport usually arrives around November 29, and the last of the season around March 17. Those are the middle dates across the winters of 1991–2020 at Attica 2E, IN, 9.9 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 36 days after the last snow.
Planting calendar for 47993
| When | What to do |
|---|---|
| February 11 – February 25 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 25 – March 11 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 25 – April 8 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 22 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 25 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 3 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 17 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 47993 is 10 miles from Attica 2E, IN, which stands at 727 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 47918 (Attica). The 2023 USDA Plant Hardiness Zone Map lists ZIP 47993 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°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.