This report describes the typical weather at the Luis Muñoz Marín International Airport (San Juan, Puerto Rico) weather station over the course of an average October. It is based on the historical records from 1992 to 2012. Earlier records are either unavailable or unreliable.
San Juan has a tropical rainforest climate with no dry season. The area within 25 mi of this station is covered by oceans and seas (48%), forests (30%), grasslands (12%), marshes (6%), and croplands (3%).
The month of October is characterized by essentially constant daily high temperatures, with daily highs around 87°F throughout the month, exceeding 91°F or dropping below 85°F only one day in ten.
Over the course of October, the length of the day is essentially constant. The shortest day of the month is October 31 with 11:28 hours of daylight; the longest day is October 1 with 11:57 hours of daylight.
The earliest sunrise is at 6:15am on October 2; the latest sunset is at 6:12pm on October 1; the latest sunrise is at 6:24am on October 31; the earliest sunset is at 5:51pm on October 31.
Daylight savings time (DST) is not observed in 2012.
The median cloud cover is 39% (mostly clear) and does not vary substantially over the course of the month.
On October 16, a representative day, the sky is clear or mostly clear 46% of the time, partly cloudy 30% of the time, and mostly cloudy or overcast 18% of the time.
The average probability that some form of precipitation will be observed in a given day is 69%, with little variation over the course of the month.
Throughout October, the most common forms of precipitation are light rain, thunderstorms, heavy rain, and moderate rain.
Light rain is the most severe precipitation observed during 36% of those days with precipitation. It is most likely around October 31, when it is observed during 27% of all days.
Thunderstorms are the most severe precipitation observed during 35% of those days with precipitation. They are most likely around October 1, when it is observed during 29% of all days.
Heavy rain is the most severe precipitation observed during 15% of those days with precipitation. It is most likely around October 31, when it is observed during 12% of all days.
Moderate rain is the most severe precipitation observed during 14% of those days with precipitation. It is most likely around October 31, when it is observed during 10% of all days.
Either snow is exceptionally unlikely to fall at this location in October or this station does not reliably report precipitation types.
The relative humidity typically ranges from 63% (mildly humid) to 91% (very humid) over the course of a typical October, rarely dropping below 55% (mildly humid) and reaching as high as 97% (very humid).
The air is driest around October 8, at which time the relative humidity drops below 68% (mildly humid) three days out of four; it is most humid around October 31, 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 October, the dew point typically varies from 71°F (very muggy) to 76°F (oppressive) and is rarely below 69°F (muggy) or above 79°F (oppressive).
Over the course of October typical wind speeds vary from 0 mph to 15 mph (calm to moderate breeze), rarely exceeding 19 mph (fresh breeze).
The highest average wind speed of 6 mph (light breeze) occurs around October 28, at which time the average daily maximum wind speed is 15 mph (moderate breeze).
The lowest average wind speed of 6 mph (light breeze) occurs around October 14, at which time the average daily maximum wind speed is 14 mph (moderate breeze).