This report describes the typical weather at the Indira Gandhi International Airport (New Delhi, 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.
New Delhi has a hot semi-arid steppe climate. The area within 25 mi of this station is covered by croplands (87%) and built-up areas (9%).
The month of September is characterized by essentially constant daily high temperatures, with daily highs around 93°F throughout the month, exceeding 99°F or dropping below 86°F only one day in ten.
Over the course of September, the length of the day is gradually decreasing. From the start to the end of the month, the length of the day decreases by 49 minutes, implying an average day-over-day decrease of 1.6 minutes.
The shortest day of the month is September 30 with 11:54 hours of daylight; the longest day is September 1 with 12:43 hours of daylight.
The earliest sunrise is at 6:00am on September 1; the latest sunset is at 6:43pm on September 1; the latest sunrise is at 6:14am on September 30; the earliest sunset is at 6:09pm on September 30.
Daylight savings time (DST) is not observed in 2012.
The median cloud cover ranges from 22% (mostly clear) to 51% (partly cloudy). The trend is for the sky to be clearing rapidly with the median cloud cover decreasing by 29% from the start to the end of the month.
On September 30, the clearest day of the month, the sky is clear, mostly clear, or partly cloudy 71% of the time, and overcast or mostly cloudy 15% of the time.
On September 1, the cloudiest day of the month, the sky is overcast, mostly cloudy, or partly cloudy 56% of the time, and clear or mostly clear 36% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around September 1, occurring in 39% of days. Precipitation is least likely around September 30, occurring in 20% of days.
Throughout September, the most common forms of precipitation are thunderstorms, light rain, and moderate rain.
Thunderstorms are the most severe precipitation observed during 64% of those days with precipitation. They are most likely around September 1, when it is observed during 25% of all days.
Light rain is the most severe precipitation observed during 16% of those days with precipitation. It is most likely around September 1, when it is observed during 7% of all days.
Moderate rain is the most severe precipitation observed during 14% of those days with precipitation. It is most likely around September 1, when it is observed during 5% 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 41% (comfortable) to 91% (very humid) over the course of a typical September, rarely dropping below 26% (dry) and reaching as high as 100% (very humid).
The air is driest around September 30, at which time the relative humidity drops below 48% (comfortable) three days out of four; it is most humid around September 12, rising above 86% (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 63°F (mildy humid) to 79°F (oppressive) and is rarely below 55°F (very comfortable) or above 82°F (very oppressive).
Over the course of September typical wind speeds vary from 0 mph to 12 mph (calm to gentle breeze), rarely exceeding 16 mph (moderate breeze).
The highest 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).
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).