This report describes the typical weather at the Cozumel International Airport (Cozumel, Mexico) weather station over the course of an average September. It is based on the historical records from 1991 to 2012. Earlier records are either unavailable or unreliable.
Cozumel has a tropical monsoon climate with short dry season. The area within 25 mi of this station is covered by oceans and seas (69%) and forests (30%).
The month of September is characterized by gradually falling daily high temperatures, with daily highs around 89°F throughout the month, exceeding 92°F or dropping below 83°F only one day in ten.
Over the course of September, the length of the day is gradually decreasing. The shortest day of the month is September 30 with 11:57 hours of daylight; the longest day is September 1 with 12:31 hours of daylight.
The earliest sunrise is at 6:32am on September 2; the latest sunset is at 7:03pm on September 1; the latest sunrise is at 6:39am on September 30; the earliest sunset is at 6:36pm on September 30.
Daylight saving 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 65% (partly 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 5% of the time, partly cloudy 18% of the time, and mostly cloudy or overcast 23% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around September 23, occurring in 41% of days. Precipitation is least likely around September 1, occurring in 36% 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 40% of those days with precipitation. It is most likely around September 3, when it is observed during 16% of all days.
Moderate rain is the most severe precipitation observed during 36% of those days with precipitation. It is most likely around September 18, when it is observed during 16% of all days.
Thunderstorms are the most severe precipitation observed during 14% of those days with precipitation. They are most likely around September 22, when it is observed during 6% 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 64% (mildly humid) to 95% (very humid) over the course of a typical September, rarely dropping below 57% (mildly humid) and reaching as high as 100% (very humid).
The air is driest around September 1, at which time the relative humidity drops below 67% (mildly humid) three days out of four; it is most humid around September 30, rising above 93% (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 74°F (very muggy) to 78°F (oppressive) and is rarely below 71°F (muggy) or above 81°F (very 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 5 mph (light 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 5 mph (light breeze) occurs around September 1, at which time the average daily maximum wind speed is 13 mph (moderate breeze).