USDA Hardiness Zone 6b
Frost Dates for 15478 — Smithfield, Pennsylvania
NOAA 1991–2020 normals from Lake Lynn, WV (900 ft), 5 miles southwest.
Updated
In Smithfield, the last spring frost (32°F) is around April 25 in half of years and has passed by May 13 in nine years out of ten. The first fall frost comes around October 24, as early as October 9 one year in ten, leaving a typical freeze-free season of 181 days (NOAA, Lake Lynn, WV).
- Last spring frost
- April 25
- First fall frost
- October 24
- Growing season
- 181 days
- Hardiness zone
- 6b
50% probability
50% probability
freeze-free, 50%
-5 to 0°F (-20.6 to -17.8°C) coldest night
- First snow
- December 9
- Last snow
- March 7
- Winters with snow
- 100%
- Snow per year
- 18.4"
median, 1991–2020
median, 1991–2020
24 of 24 observed
NOAA normal
Frost risk by date in Smithfield
Half of springs at Lake Lynn, WV see their last 32°F night by April 25; only one in ten is past it by April 9, and one in ten still has one after May 13. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 6 20%, and after May 13 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 70% 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 9 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 28, 15 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 158 one year in ten. On average 110 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 6, and return around October 12. Severe cold of 16°F or below comes every winter, usually between December 9 and March 7.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 21 | Apr 26 | Apr 30 | May 2 | May 6 | May 9 | May 13 | May 17 | May 23 |
| 32°F | Apr 9 | Apr 15 | Apr 18 | Apr 21 | Apr 25 | Apr 28 | May 1 | May 6 | May 13 |
| 28°F | Mar 26 | Mar 31 | Apr 4 | Apr 7 | Apr 11 | Apr 15 | Apr 18 | Apr 21 | Apr 28 |
| 24°F | Mar 13 | Mar 19 | Mar 24 | Mar 27 | Mar 31 | Apr 2 | Apr 5 | Apr 9 | Apr 14 |
| 20°F | Mar 1 | Mar 7 | Mar 11 | Mar 14 | Mar 17 | Mar 21 | Mar 26 | Mar 29 | Apr 2 |
| 16°F | Feb 18 | Feb 25 | Mar 1 | Mar 5 | Mar 7 | Mar 10 | Mar 14 | Mar 18 | Mar 24 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 29 | Oct 4 | Oct 6 | Oct 9 | Oct 12 | Oct 14 | Oct 18 | Oct 21 | Oct 25 |
| 32°F | Oct 9 | Oct 14 | Oct 18 | Oct 21 | Oct 24 | Oct 27 | Oct 29 | Nov 1 | Nov 5 |
| 28°F | Oct 22 | Oct 26 | Oct 30 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 13 | Nov 17 |
| 24°F | Nov 1 | Nov 5 | Nov 8 | Nov 11 | Nov 14 | Nov 16 | Nov 20 | Nov 24 | Nov 30 |
| 20°F | Nov 9 | Nov 14 | Nov 18 | Nov 21 | Nov 25 | Nov 29 | Dec 3 | Dec 9 | Dec 19 |
| 16°F | Nov 17 | Nov 24 | Nov 30 | Dec 4 | Dec 9 | Dec 15 | Dec 22 | Dec 27 | Jan 4 |
Freeze probabilities 1991–2020 at Lake Lynn, WV, 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 15478 →Compare Smithfield with another place →
Compared with the next station
The nearest other station, Grays Landing, PA, 6 miles west of Smithfield, has a last frost 3 days later (April 28), a first frost 3 days earlier (October 21), a season 6 days shorter.
When it snows in Smithfield, Pennsylvania
The first measurable snow (0.1 inch or more) in Smithfield usually arrives around December 9, and the last of the season around March 7. Those are the middle dates across the winters of 1991–2020 at Grays Landing, PA, 5.6 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 49 days after the last snow.
Planting calendar for 15478
| 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 15478 is 5 miles from Lake Lynn, WV, which stands at 900 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 15478 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°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.