This report describes the typical weather at the Riga International Airport (Riga, Latvia) weather station over the course of an average September. It is based on the historical records from 1995 to 2012. Earlier records are either unavailable or unreliable.
Riga has a humid continental climate with warm summers and no dry season. The area within 25 mi of this station is covered by croplands (43%), oceans and seas (26%), forests (15%), grasslands (10%), and built-up areas (3%).
The month of September is characterized by rapidly falling daily high temperatures, with daily highs decreasing from 69Â°F to 59Â°F over the course of the month, exceeding 78Â°F or dropping below 52Â°F only one day in ten.
Over the course of September, the length of the day is very rapidly decreasing. From the start to the end of the month, the length of the day decreases by 2:19 hours, implying an average day-over-day decrease of 4.6 minutes.
The shortest day of the month is September 30 with 11:35 hours of daylight; the longest day is September 1 with 13:54 hours of daylight.
The earliest sunrise is at 6:27am on September 1; the latest sunset is at 8:20pm on September 1; the latest sunrise is at 7:27am on September 30; the earliest sunset is at 7:01pm 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 is 90% (mostly cloudy) and does not vary substantially over the course of the month.
On September 15, a representative day, the sky is clear or mostly clear 6% of the time, partly cloudy 11% of the time, and mostly cloudy or overcast 53% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around September 30, occurring in 58% of days. Precipitation is least likely around September 1, occurring in 51% of days.
Throughout September, the most common forms of precipitation are light rain, moderate rain, and thunderstorms.
Light rain is the most severe precipitation observed during 60% of those days with precipitation. It is most likely around September 30, when it is observed during 38% of all days.
Moderate rain is the most severe precipitation observed during 18% of those days with precipitation. It is most likely around September 6, when it is observed during 11% of all days.
Thunderstorms are the most severe precipitation observed during 18% of those days with precipitation. They are most likely around September 1, when it is observed during 14% of all days.
The likelihood of snow falling is highest around September 30, occurring in 4% of days.
Either snow rarely accumulates at this location in September or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 57% (mildly humid) to 97% (very humid) over the course of a typical September, rarely dropping below 42% (comfortable) and reaching as high as 100% (very humid).
The air is driest around September 1, at which time the relative humidity drops below 66% (mildly humid) three days out of four; it is most humid around September 1, rising above 96% (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 41Â°F (dry) to 57Â°F (comfortable) and is rarely below 32Â°F (dry) or above 62Â°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 1 mph to 12 mph (calm to gentle breeze), rarely exceeding 18 mph (fresh breeze).
The highest average wind speed of 7 mph (light breeze) occurs around September 21, at which time the average daily maximum wind speed is 12 mph (gentle breeze).
The lowest average wind speed of 6 mph (light breeze) occurs around September 1, at which time the average daily maximum wind speed is 12 mph (gentle breeze).