This report describes the typical weather at the Chennai International Airport (Chennai/Madras, India) weather station over the course of an average September. It is based on the historical records from 1996 to 2012. Earlier records are either unavailable or unreliable.
Chennai/Madras has a tropical savanna climate with dry winters. The area within 25 mi of this station is covered by croplands (60%), oceans and seas (33%), built-up areas (3%), and lakes and rivers (3%).
The month of September is characterized by essentially constant daily high temperatures, with daily highs around 92°F throughout the month, exceeding 97°F or dropping below 87°F only one day in ten.
Over the course of September, the length of the day is essentially constant. The shortest day of the month is September 30 with 12:01 hours of daylight; the longest day is September 1 with 12:22 hours of daylight.
The earliest sunrise is at 5:58am on September 1; the latest sunset is at 6:20pm on September 1; the latest sunrise is at 5:59am on September 27; the earliest sunset is at 6:00pm on September 30.
Daylight savings time (DST) is not observed in 2012.
The median cloud cover ranges from 66% (partly cloudy) to 72% (partly cloudy). The trend is for the sky to be clearing with the median cloud cover decreasing by 6% from the start to the end of the month.
On September 15, a representative day, the sky is clear or mostly clear 12% of the time, partly cloudy 45% of the time, and mostly cloudy or overcast 41% of the time.
The average probability that some form of precipitation will be observed in a given day is 54%, with little variation over the course of the month.
Throughout September, the most common forms of precipitation are thunderstorms, drizzle, moderate rain, and light rain.
Thunderstorms are the most severe precipitation observed during 39% of those days with precipitation. They are most likely around September 29, when it is observed during 23% of all days.
Drizzle is the most severe precipitation observed during 28% of those days with precipitation. It is most likely around September 2, when it is observed during 17% of all days.
Moderate rain is the most severe precipitation observed during 18% of those days with precipitation. It is most likely around September 1, when it is observed during 10% of all days.
Light rain is the most severe precipitation observed during 14% of those days with precipitation. It is most likely around September 2, when it is observed during 9% 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 52% (mildly humid) to 91% (very humid) over the course of a typical September, rarely dropping below 41% (comfortable) and reaching as high as 97% (very humid).
The air is driest around September 9, at which time the relative humidity drops below 57% (mildly humid) three days out of four; it is most humid around September 30, rising above 88% (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 70°F (muggy) to 78°F (oppressive) and is rarely below 66°F (muggy) or above 80°F (oppressive).
Over the course of September typical wind speeds vary from 0 mph to 14 mph (calm to moderate breeze), rarely exceeding 18 mph (moderate breeze).
The highest average wind speed of 7 mph (light breeze) occurs around September 1, at which time the average daily maximum wind speed is 14 mph (moderate breeze).
The lowest average wind speed of 5 mph (light breeze) occurs around September 30, at which time the average daily maximum wind speed is 11 mph (gentle breeze).