USDA Hardiness Zone 6b
Frost Dates for 15126 — Imperial, Pennsylvania
NOAA 1991–2020 normals from Pittsburgh International Airport, PA (1,203 ft), 3 miles northeast.
Updated
In Imperial, the last spring frost (32°F) is around April 23 in half of years and has passed by May 12 in nine years out of ten. The first fall frost comes around October 23, as early as October 9 one year in ten, leaving a typical freeze-free season of 181 days (NOAA, Pittsburgh International Airport, PA).
- Last spring frost
- April 23
- First fall frost
- October 23
- 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
- November 15
- Last snow
- April 6
- Winters with snow
- 100%
- Snow per year
- 44.1"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Imperial
Half of springs at Pittsburgh International Airport, PA see their last 32°F night by April 23; only one in ten is past it by April 9, 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 5 20%, and after May 12 10%. The 19 days between the even-odds date and the one-in-ten date is wider than at 90% of the 176 Pennsylvania stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 23 in half of years, as early as October 9 one year in ten, and holds off past November 6 one year in ten. A hard freeze of 28°F follows 12 days later, around November 4; in spring the one-in-ten date for 28°F is April 27, 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 160 one year in ten. On average 114 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 4, and return around October 12. Severe cold of 16°F or below comes every winter, usually between December 9 and March 11.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 19 | Apr 24 | Apr 28 | May 1 | May 4 | May 8 | May 11 | May 17 | May 22 |
| 32°F | Apr 9 | Apr 15 | Apr 18 | Apr 21 | Apr 23 | Apr 27 | May 1 | May 5 | May 12 |
| 28°F | Mar 28 | Apr 2 | Apr 5 | Apr 8 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 27 |
| 24°F | Mar 15 | Mar 21 | Mar 25 | Mar 29 | Mar 31 | Apr 2 | Apr 5 | Apr 9 | Apr 14 |
| 20°F | Mar 4 | Mar 10 | Mar 15 | Mar 18 | Mar 21 | Mar 24 | Mar 27 | Mar 30 | Apr 3 |
| 16°F | Feb 22 | Feb 28 | Mar 4 | Mar 8 | Mar 11 | Mar 15 | Mar 18 | Mar 22 | Mar 27 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 30 | Oct 4 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 17 | Oct 21 | Oct 25 |
| 32°F | Oct 9 | Oct 14 | Oct 18 | Oct 21 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 6 |
| 28°F | Oct 21 | Oct 26 | Oct 30 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 13 | Nov 18 |
| 24°F | Nov 1 | Nov 5 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 21 | Nov 25 | Dec 1 |
| 20°F | Nov 9 | Nov 14 | Nov 18 | Nov 22 | Nov 26 | Nov 30 | Dec 3 | Dec 8 | Dec 14 |
| 16°F | Nov 20 | Nov 26 | Dec 1 | Dec 5 | Dec 9 | Dec 14 | Dec 19 | Dec 23 | Dec 29 |
Freeze probabilities 1991–2020 at Pittsburgh International Airport, 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 15126 →Compare Imperial with another place →
Weather by month in Imperial
July is the warmest month at Pittsburgh International Airport, PA, averaging 83°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 30% of years.
Warmth for growing adds up to 3,191 growing degree days a year (base 50°F), more than at 69% of the 176 Pennsylvania stations. 36% of them (1,133) have built up by the end of June, and July adds the most, 718. Precipitation totals 39.6 inches a year, most in July (4.3") and least in February (2.6"); 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% | 25 | 6 |
| Feb | 40 | 23 | 2.6 | 100% | 23 | 7 |
| Mar | 49 | 30 | 3.2 | 100% | 19 | 38 |
| Apr | 62 | 41 | 3.3 | 96% | 6 | 144 |
| May | 72 | 51 | 3.8 | 30% | 1 | 358 |
| Jun | 79 | 59 | 4.1 | 0% | 0 | 581 |
| Jul | 83 | 63 | 4.3 | 0% | 0 | 718 |
| Aug | 82 | 62 | 3.5 | 0% | 0 | 677 |
| Sep | 75 | 55 | 3.3 | 0% | 0 | 450 |
| Oct | 63 | 44 | 2.8 | 76% | 2 | 168 |
| Nov | 51 | 34 | 2.9 | 100% | 14 | 38 |
| Dec | 41 | 27 | 2.8 | 100% | 23 | 8 |
Monthly normals 1991–2020 at Pittsburgh International Airport, PA (1,203 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, Moon Twp, PA, 6 miles northeast of Imperial, has a last frost 5 days later (April 28), a first frost 5 days earlier (October 18), a season 9 days shorter.
When it snows in Imperial, Pennsylvania
The first measurable snow (0.1 inch or more) in Imperial usually arrives around November 15, and the last of the season around April 6. Those are the middle dates across the winters of 1991–2020 at Pittsburgh International Airport, PA, 3.3 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 17 days after the last snow.
Planting calendar for 15126
| When | What to do |
|---|---|
| February 12 – February 26 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 26 – March 12 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 26 – April 9 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 23 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 31 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 9 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 23 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 15126 is 3 miles from Pittsburgh International Airport, PA, which stands at 1,203 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 15108 (Coraopolis). The 2023 USDA Plant Hardiness Zone Map lists ZIP 15126 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.