This report describes the typical weather at the Warsaw Frederic Chopin Airport (Warsaw, Poland) weather station over the course of an average September. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Warsaw has a humid continental climate with warm summers and no dry season. The area within 25 mi of this station is covered by grasslands (52%), croplands (41%), and built-up areas (5%).
The month of September is characterized by falling daily high temperatures, with daily highs decreasing from 69°F to 60°F over the course of the month, exceeding 78°F or dropping below 52°F only one day in ten.
Over the course of September, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1:55 hours, implying an average day-over-day decrease of 3.8 minutes.
The shortest day of the month is September 30 with 11:39 hours of daylight; the longest day is September 1 with 13:34 hours of daylight.
The earliest sunrise is at 5:48am on September 1; the latest sunset is at 7:22pm on September 1; the latest sunrise is at 6:36am on September 30; the earliest sunset is at 6:15pm on September 30.
Daylight savings time is observed in 2012 but it neither starts nor ends in September, so the entire month is in daylight time.
The median cloud cover ranges from 58% (partly cloudy) to 70% (partly cloudy). The trend is for the sky to be becoming cloudier with the median cloud cover increasing by 12% from the start to the end of the month.
On September 1, the clearest day of the month, the sky is clear, mostly clear, or partly cloudy 60% of the time, and overcast or mostly cloudy 30% of the time.
On September 30, the cloudiest day of the month, the sky is overcast, mostly cloudy, or partly cloudy 62% of the time, and clear or mostly clear 29% of the time.
The average probability that some form of precipitation will be observed in a given day is 50%, with little variation over the course of the month.
Throughout September, the most common forms of precipitation are moderate rain, light rain, and thunderstorms.
Moderate rain is the most severe precipitation observed during 67% of those days with precipitation. It is most likely around September 30, when it is observed during 35% of all days.
Light rain is the most severe precipitation observed during 17% of those days with precipitation. It is most likely around September 27, when it is observed during 9% of all days.
Thunderstorms are the most severe precipitation observed during 13% of those days with precipitation. They are most likely around September 1, when it is observed during 12% of all days.
Either snow is exceptionally unlikely to fall at this location in September or this station does not reliably report precipitation types.
The relative humidity typically ranges from 55% (mildly humid) to 97% (very humid) over the course of a typical September, rarely dropping below 39% (comfortable) and reaching as high as 100% (very humid).
The air is driest around September 1, at which time the relative humidity drops below 64% (mildly humid) three days out of four; it is most humid around September 27, rising above 94% (very humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a typical September, the dew point typically varies from 42°F (dry) to 56°F (comfortable) and is rarely below 35°F (dry) or above 62°F (mildy humid).
The time of the month between September 1 and September 30 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of September typical wind speeds vary from 2 mph to 13 mph (light air to moderate breeze), rarely exceeding 19 mph (fresh breeze).
The highest average wind speed of 8 mph (gentle breeze) occurs around September 8, at which time the average daily maximum wind speed is 13 mph (moderate breeze).
The lowest average wind speed of 8 mph (gentle breeze) occurs around September 20, at which time the average daily maximum wind speed is 13 mph (moderate breeze).