Weather in Philadelphia in August

Shoulder season. August sits in between. You will get good days and you will lose some. Highs average 29.6 °C, lows 19.1 °C, and rain falls on 13 days — nothing in the month is working against you.

August ranks 6 of 12 in Philadelphia: past the worst of the year but short of September, which is the month to book if the dates are open.

Rain on 13 days, 4 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 29.6 °C days and 19.1 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: 14 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest August day reached 39.4 °C and the coldest night fell to 11.4 °C, and the wettest single day dropped 110 mm — roughly 91% of the month's rain in one day.

August is moderately variable: 51 mm in the driest year against 384 mm in the wettest, around an average of 121 mm. Roughly two Augusts in three land near that average, and the third does something else entirely.

Wind is light at 5.2 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 74%.

How August sits in the year

Temperatures hold steady either side: 30 °C in July, 29.6 here, 26.5 in September. Nothing about the timing within the month matters much.

Daylight in August

13.8 hours of daylight, losing 1.1 hours across the month. That is between Philadelphia's extremes of 15 and 9.4 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 34.9 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

August in Philadelphia versus nearby

If Philadelphia is one option among several, the nearby comparison is worth making. New York City is a better bet in August — 3.5 °C cooler, the same number of rain days. Washington is close enough to be a coin toss — within a degree on temperature, the same number of rain days.

So: August is a compromise. September is 19 points better and is what Philadelphia is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Philadelphia

See all twelve months in Philadelphia, or where else to go in August.