Do I need to cover plants for frost in Philadelphia, PA this week?
Here's the next 7 days for covering plants in Philadelphia, checked hour by hour against the published thresholds. Below it: what Philadelphia's 1991–2020 climate averages say about the months that usually work.
This week in Philadelphia
Asking the sky…
Fairsky is not a substitute for official warnings. For warnings, go to weather.gov. Verdicts are guidance, not guarantees. Your product's label always wins.
When covering plants usually works in Philadelphia
- On 1991–2020 averages, Philadelphia's median last spring freeze (32°F) comes around March 30 and the median first fall freeze around November 17. In half of years the date is later than that, in half earlier.
- Nights of 36°F or colder, when frost can form under clear, calm skies, typically end around April 8 and return around November 5.
- Hard freezes (28°F or colder, which kill most tender plants even under a cover) typically end around March 17 and return around November 29.
- Philadelphia averages 62 nights a year at or below 32°F, most of them in January (19.6).
| Month | Avg high | Avg low | Days ≥0.10" rain | Nights ≤32°F |
|---|---|---|---|---|
| January | 42° | 28° | 7.0 | 19.6 |
| February | 45° | 30° | 6.3 | 16.1 |
| March | 54° | 36° | 7.0 | 9.0 |
| April | 66° | 46° | 7.2 | 0.9 |
| May | 76° | 56° | 8.1 | 0.0 |
| June | 85° | 66° | 7.6 | 0.0 |
| July | 89° | 71° | 6.9 | 0.0 |
| August | 87° | 70° | 6.7 | 0.0 |
| September | 80° | 63° | 6.1 | 0.0 |
| October | 68° | 51° | 6.0 | 0.1 |
| November | 56° | 41° | 6.0 | 3.4 |
| December | 47° | 33° | 7.2 | 13.2 |
Station: Phila Franklin Inst (NOAA NCEI USC00366886), about 1 km from central Philadelphia. “Rain days” count days with 0.10" or more of precipitation.
The rules we check
- Cover tender plants when the overnight low is forecast at 34°F or colder.
- At 35–36°F, Fairsky still says cover when the night looks clear and calm (little cloud, wind 5 mph or less), because the ground can frost before the air hits 32°F. (Fairsky default: no source gave a number)
- 32°F or colder is a freeze.
- 28°F or colder is a hard freeze, which kills most tender vegetation; bring pots inside, since covers may not be enough.
Your product's label always wins. Labels differ by product; in the app you can enter your label's temperature range and rain-free hours, and the verdict uses them instead.
Sources: NWS glossary: frost advisory · NWS glossary: hard freeze
More home and yard jobs in Philadelphia
- Stain a deckDeck and fence stain: 50–90°F, dry wood, 24 rain-free hours after.
- Paint a house exteriorExterior latex paint: 40°F and up, 5°F above the dew point, 4 dry hours after.
- Pour concreteConcrete: 40–85°F, no rain for 24 hours, no freezing for 48.
- Spray weedsWeed killer: 3–10 mph wind, 45–85°F, 4 rain-free hours after.
- Apply pre-emergentCrabgrass pre-emergent: before soil holds 55°F (about 200 GDD), then water it in.
- Plant grass seedCool-season grass seed: soil about 50–65°F, highs 60–80°F, no washout rain.
- Seal a drivewayAsphalt sealcoat: 55°F and rising, 50°F overnight, 36 rain-free hours.
The app covers 47 activities in all, from mowing to a round of golf: see every activity and its rules.
Cover plants for frost in nearby cities
- Allentown, PA48 miles away
- Lancaster, PA61 miles away
- New York, NY81 miles away
- Baltimore, MD90 miles away
- Harrisburg, PA94 miles away
- Scranton, PA104 miles away
All cover plants for frost cities: Cover plants for frost, by city · Home and yard in Pennsylvania
Questions
How is this verdict made?
We take the National Weather Service hourly forecast for Philadelphia and check each hour against the thresholds listed above. The result is guidance, not a guarantee; your product's label always wins.
Will it frost tonight in Philadelphia?
Frost is possible when the forecast low is in the mid-30s °F or colder, especially on clear, calm nights. The verdict above checks Philadelphia's low tonight and this week.
Fairsky is not a substitute for official warnings. For warnings, go to weather.gov.
Live forecasts: National Weather Service / NOAA (public domain), fetched by your browser. Climate averages: NOAA NCEI U.S. Climate Normals, 1991–2020 (public domain). Activity thresholds: product data sheets, ACI and university extension guidance, linked on each page; your product’s label wins.