Pennsylvania weather and outdoor projects
Pennsylvania has humid summers and cold winters, with Philadelphia milder than Pittsburgh and the central mountains. Pittsburgh and western Pennsylvania are among the cloudiest places in the East, which slows drying in spring and fall.
Late May, June and September are usually the best months for staining and painting. Summer storms and humid nights bring dew on fresh finishes. Winters have many freeze-thaw cycles and road salt, so proper concrete curing and sealing matter, and driveway sealing is best finished by early October.
Frost dates in Pennsylvania
In Philadelphia, the median last spring freeze (32°F) is around April 2 and the median first fall freeze is around November 10, a frost-free season of about 224 days.
In Pittsburgh, the median last spring freeze (32°F) is around April 23 and the median first fall freeze is around October 23, a frost-free season of about 181 days.
Frost dates matter for concrete, which must not freeze in its first 48 hours, for paint and caulk that need nights above their minimum, and for lawn care, since crabgrass preventer goes down as the soil warms in spring. See how late in fall you can stain, paint or seal.
Best time to stain a deck in Pennsylvania
In Philadelphia, the most reliable months are May–June and August–October. April, July and November can also work on the right days. December–March is too cold, with average highs around 46°F. In April, nights average about 44°F, so finish early on mild days and check the overnight low. July is hot, with highs near 88°F, so start early and keep out of full afternoon sun. November is cool, with highs around 56°F, so choose the warmest afternoons.
In Pittsburgh, the most reliable months are May–September. April and October can also work on the right days. November–March is too cold, with average highs around 43°F. In April and October, nights average about 42°F, so finish early on mild days and check the overnight low.
Check this week’s hour-by-hour verdict with the deck staining forecast.
Best time to paint outside in Pennsylvania
In Philadelphia, the most reliable months are May–June and August–October. March–April, July and November can also work on the right days. December–February is too cold, with average highs around 44°F. March and November are cool, with highs around 54°F, so choose the warmest afternoons. In April, nights average about 44°F, so finish early on mild days and check the overnight low. July is hot, with highs near 88°F, so start early and keep out of full afternoon sun.
In Pittsburgh, the most reliable months are May–September. April and October–November can also work on the right days. December–March is too cold, with average highs around 41°F. In April and October, nights average about 42°F, so finish early on mild days and check the overnight low. November is cool, with highs around 51°F, so choose the warmest afternoons.
Check this week’s hour-by-hour verdict with the exterior painting forecast.
Best time to pour concrete in Pennsylvania
In Philadelphia, the most reliable months are April–October. November can also work on the right days. December–March averages about 18 nights a month at or below 32°F, so fresh concrete needs blankets or heated enclosures. November brings about 5 freezing nights a month, so pick a mild spell and keep curing blankets on hand.
In Pittsburgh, the most reliable months are May–September. April and October can also work on the right days. November–March averages about 21 nights a month at or below 32°F, so fresh concrete needs blankets or heated enclosures. April and October bring about 4 freezing nights a month, so pick a mild spell and keep curing blankets on hand.
Check this week’s hour-by-hour verdict with the concrete pouring forecast.
Best time to seal a driveway in Pennsylvania
In Philadelphia, the most reliable months are May–September. April and October can also work on the right days. November–March is too cold, with average highs around 48°F. April and October are cool, with highs around 66°F, so choose the warmest afternoons.
In Pittsburgh, the most reliable months are June–September. May and October can also work on the right days. November–March is too cold, with average highs around 43°F. In April, nights average about 41°F, too cold for the coating to dry and cure overnight. In May, nights average about 51°F, so finish early on mild days and check the overnight low. October is cool, with highs around 63°F, so choose the warmest afternoons.
Check this week’s hour-by-hour verdict with the driveway sealing forecast.
Best time to fertilize or treat a lawn in Pennsylvania
In Philadelphia, the most reliable months are April–June and August–October. March, July and November can also work on the right days. December–February is too cold, with average highs around 44°F. March and November are cool, with highs around 54°F, so choose the warmest afternoons. July is hot, with highs near 88°F, so start early and keep out of full afternoon sun.
In Pittsburgh, the most reliable months are April–October. November can also work on the right days. December–March is too cold, with average highs around 41°F. November is cool, with highs around 51°F, so choose the warmest afternoons.
Check this week’s hour-by-hour verdict with the lawn fertilizer forecast.
How the weather differs across Pennsylvania
| Place | Hottest month avg high | Coldest month avg low | Rain per year | Last spring freeze | First fall freeze |
|---|---|---|---|---|---|
| Philadelphia | 88°F | 26°F | 44 in | April 2 | November 10 |
| Pittsburgh | 83°F | 21°F | 40 in | April 23 | October 23 |
Of the places above, Philadelphia has the most good months for staining, painting and concrete combined (17 job-months), and Pittsburgh has the fewest (15). If you live between them, expect something in between, and higher ground to be cooler with a shorter season.
Monthly weather in Philadelphia
| Month | Avg high | Avg low | Wet days* | Rain | 3 PM humidity | Freezing nights |
|---|---|---|---|---|---|---|
| January | 41°F | 26°F | 6 | 3.1 in | 51% | 23 |
| February | 44°F | 28°F | 6 | 2.8 in | 46% | 20 |
| March | 53°F | 34°F | 7 | 4.0 in | 43% | 12 |
| April | 65°F | 44°F | 6 | 3.5 in | 41% | 1 |
| May | 74°F | 54°F | 6 | 3.3 in | 45% | 0 |
| June | 83°F | 64°F | 7 | 4.0 in | 47% | 0 |
| July | 88°F | 70°F | 6 | 4.4 in | 47% | 0 |
| August | 86°F | 68°F | 6 | 4.3 in | 49% | 0 |
| September | 79°F | 61°F | 6 | 4.4 in | 50% | 0 |
| October | 67°F | 49°F | 6 | 3.5 in | 50% | 0 |
| November | 56°F | 39°F | 6 | 2.9 in | 49% | 5 |
| December | 46°F | 31°F | 7 | 4.0 in | 53% | 17 |
*Days with at least 0.1 inch of rain or melted snow. Freezing nights: average nights a month at or below 32°F. Humidity is calculated from NOAA hourly normal temperature and dew point at 3 PM.
Monthly weather in Pittsburgh
| Month | Avg high | Avg low | Wet days* | Rain | 3 PM humidity | Freezing nights |
|---|---|---|---|---|---|---|
| January | 36°F | 21°F | 7 | 3.0 in | 62% | 25 |
| February | 40°F | 23°F | 7 | 2.6 in | 56% | 23 |
| March | 49°F | 30°F | 8 | 3.1 in | 49% | 19 |
| April | 62°F | 41°F | 9 | 3.3 in | 43% | 6 |
| May | 72°F | 51°F | 8 | 3.8 in | 47% | 1 |
| June | 79°F | 59°F | 8 | 4.1 in | 51% | 0 |
| July | 83°F | 63°F | 7 | 4.3 in | 51% | 0 |
| August | 82°F | 62°F | 6 | 3.5 in | 50% | 0 |
| September | 75°F | 55°F | 6 | 3.3 in | 51% | 0 |
| October | 63°F | 44°F | 7 | 2.8 in | 51% | 2 |
| November | 51°F | 34°F | 7 | 2.9 in | 54% | 14 |
| December | 41°F | 27°F | 7 | 2.8 in | 62% | 23 |
Use the averages, then check the forecast
These ratings describe a typical month, not a particular week. A warm spell in a “poor” month can give you a good day, and a wet week can spoil a “good” one. Use this page to plan the season, then check the 7-day forecast for your ZIP code before you buy materials or book help. Each project forecast checks the hours after you finish too: overnight lows, dew and rain that would ruin fresh stain, paint, sealer or concrete.
About this data
Monthly temperatures, rain days, snowfall and freeze dates are NOAA National Centers for Environmental Information (NCEI) U.S. Climate Normals for 1991–2020 at PHILADELPHIA INTL AP, PITTSBURGH INTL AP. Ratings apply the same temperature limits as our forecasts (for example, 50°F or warmer for deck stain and driveway sealer, and no freezing nights for new concrete) to the average month. Your product label always takes priority.
Frequently asked questions
When is the best time to stain a deck in Pennsylvania?
In Philadelphia, May–June and August–October. In Pittsburgh, May–September. Look for at least 24 dry hours before and after, and nights above about 40°F. The deck staining forecast checks your exact week.
When is the last frost in Pennsylvania?
Philadelphia: around April 2; Pittsburgh: around April 23. These are median dates from NOAA 1991–2020 normals, so a freeze after them happens in about half of years. Low spots and valleys freeze later in spring.
Can you pour concrete in winter in Pennsylvania?
Yes, but it needs cold-weather practices. Philadelphia averages about 59 freezing nights from December to February, so fresh concrete needs insulated blankets, a heated enclosure or an accelerated mix, and must not freeze in the first 48 hours. Many homeowners wait for spring.
What months are best for sealing a driveway in Pennsylvania?
In Philadelphia, May–September. In Pittsburgh, June–September. Most sealers need 50°F or warmer for 24 hours and a dry day after. See the driveway sealing forecast.