This report describes the typical weather at the Pittsburgh International Airport (Pittsburgh, Pennsylvania, United States) weather station over the course of an average September 8. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Pittsburgh, Pennsylvania has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by forests (78%) and built-up areas (19%).
The temperature typically varies from 59°F to 75°F and is rarely below 49°F or above 84°F.
The coolest hours of the day are from 2am to 9am with the coldest at 7am, at which time the temperature is below 64°F three days out of four.
The warmest hours of the day are from noon to 7pm with the hottest at 4pm, at which time the temperature is above 70°F three days out of four.
The day has gained half its heat by 11am and lost it again by 10pm.
On September 8 the Sun rises at 6:55am and sets at 7:40pm.
Solar noon is at 1:18pm.
For reference, on the longest day of the year the Sun rises at 5:50am and sets at 8:54pm, while on the shortest day of the year it rises at 7:40am and sets at 4:57pm.
Astronomical twilight begins and ends 94 minutes before sunrise and after sunset at 5:21am and 9:15pm, respectively.
Nautical twilight begins and ends 60 minutes before sunrise and after sunset at 5:54am and 8:41pm, respectively.
Civil twilight begins and ends 27 minutes before sunrise and after sunset at 6:27am and 8:08pm, respectively.
Solar twilight begins and ends 36 minutes after sunrise and before sunset at 7:31am and 7:04pm, respectively.
The median cloud cover ranges from 53% (partly cloudy) to 77% (partly cloudy).
At 1am, the clearest time of the day, the sky is clear, mostly clear, or partly cloudy 59% of the time, and overcast or mostly cloudy 40% of the time.
At 1pm, the cloudiest time of the day, the sky is overcast, mostly cloudy, or partly cloudy 76% of the time, and clear or mostly clear 24% of the time.
The sky is typically clearing in earnest by 8pm.
The clouds have typically started forming in earnest by 7am.
There is a 43% chance that precipitation will be observed at some point during the day.
The average measured liquid-equivalent quantity of precipitation is 0.104". Among only those days for which there is at least some measured precipitation, the average is 0.327" and the total rarely exceeds 0.700".
When precipitation does occur it is most often in the form of slight rain (38% of days with precipitation have at worst slight rain), moderate rain (29%), and thunderstorms (26%).
Precipitation is most likely around 10am and least likely around 1am.
Either snow is exceptionally unlikely to fall at this location on September 8 or this station does not reliably report precipitation types.
The relative humidity typically ranges from 56% (mildly humid) to 86% (very humid), rarely dropping below 38% (comfortable), or exceeding 96% (very humid).
The air is driest at 4pm, at which time the relative humidity is less than 65% (mildly humid) three days out of four; it is most humid at 6am, exceeding 81% (humid) three days out of four.
The dew point ranges from 55°F to 58°F with an average of 56°F.
For reference, comfortable indoor conditions should have a relative humidity between 30% and 50% with a dew point of less than 65°F.
Sustained wind speeds typically vary from 4 mph to 9 mph (light breeze to gentle breeze) over the course of the day.
The peak sustained wind speed typically occurs around 3pm and is rarely outside the range 4 mph to 15 mph (light breeze to moderate breeze).
The wind is most calm around 4am, rarely exceeding 9 mph (gentle breeze).
The wind is most often out of the west (13% of the time), south west (13% of the time), south (12% of the time), and north (11% of the time).