USDA Hardiness Zone 6a
Frost Dates for 16833 — Curwensville, Pennsylvania
NOAA 1991–2020 normals from Grampian 1E, PA (1,510 ft), 2 miles northwest.
Updated
In Curwensville, the last spring frost (32°F) is around May 4 in half of years and has passed by May 21 in nine years out of ten. The first fall frost comes around October 13, as early as September 30 one year in ten, leaving a typical freeze-free season of 160 days (NOAA, Grampian 1E, PA).
- Last spring frost
- May 4
- First fall frost
- October 13
- Growing season
- 160 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 15
- Last snow
- April 8
- Winters with snow
- 100%
- Snow per year
- 63"
median, 1991–2020
median, 1991–2020
16 of 16 observed
NOAA normal
Frost risk by date in Curwensville
Half of springs at Grampian 1E, PA see their last 32°F night by May 4; only one in ten is past it by April 20, and one in ten still has one after May 21. Planting tender crops after May 11 leaves a 30% risk of a frost on them, after May 15 20%, and after May 21 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 13 in half of years, as early as September 30 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 14 days later, around October 27; in spring the one-in-ten date for 28°F is May 10, 11 days before the 32°F one. The freeze-free season lasts 160 days in a typical year, shorter than at 73% of the 176 Pennsylvania stations; it reaches 182 days one year in ten and falls short of 138 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 12 days longer, to about May 16, and return around October 1. Severe cold of 16°F or below comes every winter, usually between December 1 and March 21.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 30 | May 4 | May 9 | May 13 | May 16 | May 20 | May 23 | May 26 | May 30 |
| 32°F | Apr 20 | Apr 25 | Apr 28 | Apr 30 | May 4 | May 7 | May 11 | May 15 | May 21 |
| 28°F | Apr 6 | Apr 12 | Apr 16 | Apr 19 | Apr 23 | Apr 26 | Apr 30 | May 4 | May 10 |
| 24°F | Mar 26 | Mar 31 | Apr 3 | Apr 6 | Apr 8 | Apr 11 | Apr 15 | Apr 19 | Apr 24 |
| 20°F | Mar 15 | Mar 20 | Mar 24 | Mar 27 | Mar 30 | Apr 1 | Apr 4 | Apr 7 | Apr 12 |
| 16°F | Mar 5 | Mar 10 | Mar 15 | Mar 18 | Mar 21 | Mar 24 | Mar 27 | Mar 30 | Apr 3 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 19 | Sep 23 | Sep 25 | Sep 28 | Oct 1 | Oct 2 | Oct 5 | Oct 8 | Oct 12 |
| 32°F | Sep 30 | Oct 3 | Oct 6 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 23 | Oct 28 |
| 28°F | Oct 11 | Oct 15 | Oct 20 | Oct 23 | Oct 27 | Oct 30 | Nov 2 | Nov 5 | Nov 10 |
| 24°F | Oct 25 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 15 | Nov 18 | Nov 23 |
| 20°F | Nov 6 | Nov 11 | Nov 14 | Nov 17 | Nov 20 | Nov 23 | Nov 27 | Dec 1 | Dec 6 |
| 16°F | Nov 14 | Nov 19 | Nov 24 | Nov 27 | Dec 1 | Dec 4 | Dec 7 | Dec 12 | Dec 18 |
Freeze probabilities 1991–2020 at Grampian 1E, 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 16833 →Compare Curwensville with another place →
Compared with the next station
The nearest other station, Clearfield Lawrence Airport, PA, 10 miles northeast of Curwensville, has the same 50% last-frost date, a first frost 2 days earlier (October 11), a season 1 day longer.
When it snows in Curwensville, Pennsylvania
The first measurable snow (0.1 inch or more) in Curwensville usually arrives around November 15, and the last of the season around April 8. Those are the middle dates across the winters of 1991–2020 at Grampian 1E, PA, 2.2 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 26 days after the last snow.
Planting calendar for 16833
| When | What to do |
|---|---|
| February 23 – March 9 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 9 – March 23 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 6 – April 20 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 4 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 16833 is 2 miles from Grampian 1E, PA, which stands at 1,510 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 16833 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.