USDA Hardiness Zone 6a
Frost Dates for 17771 — Trout Run, Pennsylvania
NOAA 1991–2020 normals from Williamsport 2, PA (525 ft), 13 miles south.
Updated
In Trout Run, the last spring frost (32°F) is around April 25 in half of years and has passed by May 12 in nine years out of ten. The first fall frost comes around October 24, as early as October 8 one year in ten, leaving a typical freeze-free season of 181 days (NOAA, Williamsport 2, PA).
- Last spring frost
- April 25
- First fall frost
- October 24
- Growing season
- 181 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 19
- Last snow
- March 26
- Winters with snow
- 100%
- Snow per year
- 32.6"
median, 1991–2020
median, 1991–2020
21 of 21 observed
NOAA normal
Frost risk by date in Trout Run
Half of springs at Williamsport 2, PA see their last 32°F night by April 25; only one in ten is past it by April 10, and one in ten still has one after May 12. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 6 20%, and after May 12 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 50% of the 176 Pennsylvania stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 24 in half of years, as early as October 8 one year in ten, and holds off past November 5 one year in ten. A hard freeze of 28°F follows 11 days later, around November 4; in spring the one-in-ten date for 28°F is April 25, 17 days before the 32°F one. The freeze-free season lasts 181 days in a typical year, longer than at 65% of the 176 Pennsylvania stations; it reaches 202 days one year in ten and falls short of 161 one year in ten. On average 118 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 12 days longer, to about May 7, and return around October 11. Severe cold of 16°F or below comes every winter, usually between December 9 and March 10.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 21 | Apr 26 | Apr 30 | May 3 | May 7 | May 11 | May 14 | May 18 | May 23 |
| 32°F | Apr 10 | Apr 15 | Apr 19 | Apr 22 | Apr 25 | Apr 28 | May 1 | May 6 | May 12 |
| 28°F | Mar 29 | Apr 1 | Apr 4 | Apr 7 | Apr 10 | Apr 14 | Apr 17 | Apr 21 | Apr 25 |
| 24°F | Mar 15 | Mar 20 | Mar 25 | Mar 28 | Mar 30 | Apr 1 | Apr 3 | Apr 6 | Apr 10 |
| 20°F | Mar 4 | Mar 9 | Mar 13 | Mar 16 | Mar 19 | Mar 23 | Mar 27 | Mar 29 | Apr 1 |
| 16°F | Feb 21 | Feb 28 | Mar 4 | Mar 7 | Mar 10 | Mar 13 | Mar 16 | Mar 20 | Mar 25 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 29 | Oct 2 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 17 | Oct 20 | Oct 25 |
| 32°F | Oct 8 | Oct 12 | Oct 16 | Oct 20 | Oct 24 | Oct 27 | Oct 31 | Nov 2 | Nov 5 |
| 28°F | Oct 20 | Oct 27 | Oct 31 | Nov 2 | Nov 4 | Nov 6 | Nov 9 | Nov 13 | Nov 18 |
| 24°F | Nov 2 | Nov 5 | Nov 8 | Nov 12 | Nov 15 | Nov 18 | Nov 21 | Nov 25 | Dec 1 |
| 20°F | Nov 10 | Nov 16 | Nov 20 | Nov 23 | Nov 26 | Nov 30 | Dec 2 | Dec 6 | Dec 14 |
| 16°F | Nov 21 | Nov 28 | Dec 1 | Dec 4 | Dec 9 | Dec 14 | Dec 18 | Dec 23 | Dec 29 |
Freeze probabilities 1991–2020 at Williamsport 2, PA, 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 17771 →Compare Trout Run with another place →
Weather by month in Trout Run
July is the warmest month at Williamsport 2, PA, averaging 86°F by day and 63°F at night; January is the coldest at 36°F and 21°F. A freezing night is all but certain in every month from November 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 33% of years.
Warmth for growing adds up to 3,226 growing degree days a year (base 50°F), more than at 73% of the 176 Pennsylvania stations. 34% of them (1,109) have built up by the end of June, and July adds the most, 756. Precipitation totals 42.7 inches a year, most in September (4.5") and least in February (2.4"); May to September bring 48% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 36 | 21 | 3.0 | 100% | 27 | 0 |
| Feb | 39 | 22 | 2.4 | 100% | 24 | 1 |
| Mar | 49 | 29 | 3.3 | 100% | 20 | 18 |
| Apr | 63 | 39 | 3.6 | 98% | 6 | 120 |
| May | 74 | 50 | 3.8 | 33% | 1 | 366 |
| Jun | 81 | 59 | 3.9 | 0% | 0 | 605 |
| Jul | 86 | 63 | 4.3 | 0% | 0 | 756 |
| Aug | 84 | 62 | 3.8 | 0% | 0 | 711 |
| Sep | 76 | 55 | 4.5 | 1% | 0 | 466 |
| Oct | 64 | 43 | 3.7 | 72% | 3 | 160 |
| Nov | 51 | 33 | 3.1 | 100% | 14 | 21 |
| Dec | 40 | 26 | 3.3 | 100% | 24 | 3 |
Monthly normals 1991–2020 at Williamsport 2, PA (525 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, Williamsport, PA, 15 miles southeast of Trout Run, has a last frost 1 day earlier (April 24), a first frost 1 day earlier (October 23), a season 1 day shorter.
When it snows in Trout Run, Pennsylvania
The first measurable snow (0.1 inch or more) in Trout Run usually arrives around November 19, and the last of the season around March 26. Those are the middle dates across the winters of 1991–2020 at Williamsport 2, PA, 13.3 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 30 days after the last snow.
Planting calendar for 17771
| 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 August 1 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 10 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 24 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 17771 is 13 miles from Williamsport 2, PA, which stands at 525 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 17701 (Williamsport). The 2023 USDA Plant Hardiness Zone Map lists ZIP 17771 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.
Frost dates across Pennsylvania →
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.