Philadelphia weather by month — averages, rainfall & climate trends
The cradle of American independence sits in the Mid-Atlantic between coast and country, working through four full seasons — humid summers, crisp colourful autumns, and winters that swing from mild to snowbound. Average temperatures and rainfall by month, a climate graph, today's conditions versus the long-term average, and how the climate has shifted since 1940 — all on one page for Philadelphia, United States.
Today vs average
−0.9°Cabout average
How it’s changed
Right now
What it's doing today vs the historical average for this date.
Right now
18.5°
30°16°
30°22°
29°22°28°17°30°19°32°21°33°21°On this date — July 20
About average
- Record high: 37.6° · 1991
- Record low: 14.5° · 1965
- One year ago: 31.3°
Every July 20 in history — coldest to hottest
Dots show daily highs (top) and lows (bottom) for each July 20 on record (n = 86). Outlined dots are today's forecast.
Area we sample
Each city's history comes from one ERA5 grid cell — about 28 km across, shown by the dashed box. Near mountains or coasts, conditions can vary across the cell.
Location & data
Historical weather for Philadelphia is sampled from the ECMWF ERA5 reanalysis at 39.95°N, 75.16°W, with daily records since 1940.
- Coordinates
- 39.95°N, 75.16°W
- Time zone
- America/New York
- Period
- 1940–2026
- Data source
- ERA5 (ECMWF)
Last 30 days
16 of the last 30 days were warmer than the historical average for that date. Average difference: +1.1°C.
Each bar is one day, from morning low to afternoon high. Warm-colored bars are days whose mean ran above average; cool bars ran below. The dot inside the bar is the daily mean. The shaded band is the typical 10–90% range expected for that date. Average = the day's mean temperature averaged across every year of record (1940–2026) for that calendar date.
This date over the years
One dot per year — the mean temperature on this calendar date. Dots are warmer or cooler than the long-term average (dashed line); the shaded band is the typical 10–90% range, and the highlighted dot is today's forecast. Based on ERA5 reanalysis — modelled estimates, not station readings.
Weather by month
Average temperatures and rainfall for each month — what a typical year looks like, from the full record.Climate overview
Philadelphia lies at the northern edge of the humid subtropical zone (Köppen Cfa) and is one of the cooler examples of that climate. Set in the Mid-Atlantic between the Atlantic coast and the interior, it has four clearly marked seasons: hot, muggy summers, mild spring and autumn, and moderately cold winters — noticeably colder and snowier than most cities of its climate type.
Summer brings frequent humid spells, with heat and high humidity that push the heat index up on many days. Winters are the wild card: snowfall is highly variable — some years stay light while others bring major snowstorms — and lasting snow cover on the ground is rare. It is this swing between sticky summers and unpredictable winters, more than any single extreme, that defines the city's year.
The warmest month is July, with a daily mean around 25.2°C and typical afternoon highs of 30.2°C. On about 70 nights a year, the temperature never drops below 20°C. The coolest month is January, when daily means fall to about 0.5°C and overnight lows sit around -2.8°C. Around 60 days a year dip below freezing.
In total, Philadelphia averages about 1118 mm of precipitation a year; July is usually the wettest month (104 mm) and February the driest (79 mm).
The record here starts in 1940, and since then the annual mean in Philadelphia has climbed 1.7°C from the first ten years to the last ten. The count of days past 30°C has risen from roughly 35 a year to 55 between the record's first and last decades.
Climate graph (climograph)
July is the warmest month, January the coolest — a yearly swing of 25°C. Wettest month: July (~104 mm). Whole year averages ~1118 mm of rain.
Bars = average monthly rainfall (right axis). Lines = average daily high and low (left axis). Average = each month's value averaged across every year of record (1940–2026).
Monthly wind
Average daily peak wind at 10 m, by month.
Monthly solar energy
Average daily incoming solar energy in megajoules per square metre — a measured proxy for how sunny the month is.
Philadelphia month by month — what to expect
Typical conditions for each month, averaged across the full record (since 1940). Daylight is the time from sunrise to sunset. Record high/low are the most extreme values in the ERA5 dataset (modelled since 1940), so they can differ from official weather-station readings.
| Month | Avg high | Avg low | Rain | Daylight | Record high | Record low |
|---|---|---|---|---|---|---|
| January | 4.6° | -2.8° | 84 mm | 9.5 h | 22.7° (2007) | -25.2° (1984) |
| February | 6.3° | -2.0° | 79 mm | 10.5 h | 25.8° (2018) | -22.1° (1979) |
| March | 11.4° | 2.1° | 102 mm | 11.7 h | 31.3° (1998) | -17.3° (1984) |
| April | 17.7° | 7.5° | 98 mm | 13.1 h | 35.1° (2002) | -7.2° (1982) |
| May | 23.2° | 13.0° | 99 mm | 14.2 h | 35.6° (1996) | 1.4° (1966) |
| June | 27.9° | 17.9° | 91 mm | 14.8 h | 39.3° (2011) | 6.5° (1972) |
| July | 30.2° | 20.9° | 104 mm | 14.6 h | 41.2° (2011) | 11.4° (1988) |
| August | 29.0° | 20.0° | 102 mm | 13.6 h | 39.6° (2001) | 8.1° (1986) |
| September | 25.3° | 16.2° | 92 mm | 12.2 h | 38.7° (1953) | 2.5° (1963) |
| October | 19.3° | 9.9° | 83 mm | 10.9 h | 35.5° (2019) | -3.1° (1972) |
| November | 13.0° | 4.5° | 88 mm | 9.7 h | 29.4° (1950) | -9.1° (1955) |
| December | 6.8° | -0.4° | 96 mm | 9.2 h | 23.2° (1998) | -18.9° (1963) |
How it has changed
Year-by-year signals from 1940 to today.Climate stripes
Annual mean shifted from 1940–1949 to 2016–2025 by +1.7°C.
Each vertical stripe is one year. Color encodes how much that year's annual mean differed from the long-term average. Average = each year's annual mean compared to the average of all years (1940–2026). cooler ← → warmer
Annual mean temperature
Long-term trend: +0.20°C per decade.
One point per year — the temperature averaged across the whole year. The dashed line is the least-squares long-term trend. Based on ERA5 reanalysis — modelled estimates, not station readings.
Seasonal warming
Dec–Feb is warming fastest: +0.27°C per decade.
Each faint line is one three-month period's average per year; the bold dashed line is its long-term trend. Different parts of the year often warm at different rates. Based on ERA5 reanalysis — modelled estimates, not station readings.
Hot days vs frost days
Days ≥ 30°C per year: 34.8 early in the record → 53.6 recently. Frost days: 80 → 60.
Thin lines are raw yearly counts; thick lines are the smoothed trend that removes year-to-year noise. The hot-day threshold is auto-picked per city so the line actually moves. Average = a centered 5-year rolling average to smooth weather noise.
Yearly hot & cold extremes
All-time high in 2011, all-time low in 1984: 41.2°C / -25.2°C.
One point per year — the single hottest and coldest day recorded that year.
Annual rainfall
~1118 mm/year on average. Last decade ran +6% vs that average. Long-term trend: +10 mm per decade.
One bar per year of total rainfall. Dashed line is the long-term average. Average = the average annual rainfall across every year of record (1940–2026).
Day-by-day grid
Each tiny square is one calendar day across the full record — ~30,000 days per city. Use the mode switch above the chart: Anomaly colors each day by how far it ran from the historical average for that date (red = warmer, blue = cooler), Daily mean temp shows the absolute mean temperature for the day (useful to see seasons and heatwaves), and Precipitation shows daily rainfall (useful to spot wet/dry seasons and droughts). Average = the long-term average for that calendar date (1940–2026).