This report describes the typical weather at the Louis Armstrong International Airport (New Orleans, Louisiana, United States) 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.
New Orleans, Louisiana has a warm humid temperate climate with hot summers and no dry season. The area within 25 mi of this station is covered by croplands (45%), oceans and seas (26%), lakes and rivers (12%), built-up areas (5%), and forests (5%).
The month of September is characterized by falling daily high temperatures, with daily highs decreasing from 89°F to 83°F over the course of the month, exceeding 93°F or dropping below 76°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 51 minutes, implying an average day-over-day decrease of 1.7 minutes.
The shortest day of the month is September 30 with 11:54 hours of daylight; the longest day is September 1 with 12:45 hours of daylight.
The earliest sunrise is at 6:38am on September 1; the latest sunset is at 7:23pm on September 1; the latest sunrise is at 6:54am on September 30; the earliest sunset is at 6:47pm 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 45% (partly cloudy) to 54% (partly cloudy). The trend is for the sky to be clearing with the median cloud cover decreasing by 9% from the start to the end of the month.
On September 15, a representative day, the sky is clear or mostly clear 42% of the time, partly cloudy 22% of the time, and mostly cloudy or overcast 34% 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 50% of days. Precipitation is least likely around September 30, occurring in 36% of days.
Throughout September, the most common forms of precipitation are thunderstorms, moderate rain, and light rain.
Thunderstorms are the most severe precipitation observed during 50% of those days with precipitation. They are most likely around September 1, when it is observed during 29% of all days.
Moderate rain is the most severe precipitation observed during 25% of those days with precipitation. It is most likely around September 3, when it is observed during 11% of all days.
Light rain is the most severe precipitation observed during 19% of those days with precipitation. It is most likely around September 30, 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 53% (mildly humid) to 93% (very humid) over the course of a typical September, rarely dropping below 37% (comfortable) and reaching as high as 100% (very humid).
The air is driest around September 29, at which time the relative humidity drops below 61% (mildly humid) three days out of four; it is most humid around September 2, rising above 90% (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 60°F (comfortable) to 76°F (very muggy) and is rarely below 48°F (dry) or above 79°F (oppressive).
Over the course of September typical wind speeds vary from 0 mph to 13 mph (calm to moderate breeze), rarely exceeding 19 mph (fresh breeze).
The highest average wind speed of 8 mph (gentle breeze) occurs around September 30, at which time the average daily maximum wind speed is 13 mph (moderate 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 13 mph (moderate breeze).