Average Weather in September in San José Costa Rica
In San José, the month of September is characterized by essentially constant daily high temperatures, with daily highs around 77°F throughout the month, rarely exceeding 81°F or dropping below 74°F.
Daily low temperatures are around 63°F, rarely falling below 61°F or exceeding 66°F. The lowest daily average low temperature is 63°F on September 21.
For reference, on April 8, the hottest day of the year, temperatures in San José typically range from 64°F to 81°F, while on September 21, the coldest day of the year, they range from 63°F to 77°F.
Average High and Low Temperature in September
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on September. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature in September
The month of September in San José experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 94% throughout the month.
The clearest day of the month is September 13, with clear, mostly clear, or partly cloudy conditions 6% of the time.
For reference, on June 5, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 96%, while on January 2, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 64%.
Cloud Cover in September
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In San José, the chance of a wet day over the course of September is gradually increasing, starting the month at 47% and ending it at 50%.
For reference, the year's highest daily chance of a wet day is 51% on October 7, and its lowest chance is 7% on March 16.
Probability of Precipitation in September
The average sliding 31-day rainfall during September in San José is increasing, starting the month at 5.8 inches, when it rarely exceeds 10.2 inches or falls below 2.1 inches, and ending the month at 6.4 inches, when it rarely exceeds 12.0 inches or falls below 2.5 inches.
Average Monthly Rainfall in September
Over the course of September in San José, the length of the day is gradually decreasing. From the start to the end of the month, the length of the day decreases by 16 minutes, implying an average daily decrease of 32 seconds, and weekly decrease of 3 minutes, 47 seconds.
The shortest day of the month is September 30, with 12 hours, 2 minutes of daylight and the longest day is September 1, with 12 hours, 18 minutes of daylight.
Hours of Daylight and Twilight in September
The latest sunrise of the month in San José is 5:27 AM on September 1 and the earliest sunrise is 2 minutes, 11 seconds earlier at 5:24 AM on September 30.
The latest sunset is 5:45 PM on September 1 and the earliest sunset is 18 minutes earlier at 5:27 PM on September 30.
Daylight saving time is not observed in San José during 2017.
For reference, on June 21, the longest day of the year, the Sun rises at 5:17 AM and sets 12 hours, 42 minutes later, at 5:59 PM, while on December 21, the shortest day of the year, it rises at 5:48 AM and sets 11 hours, 33 minutes later, at 5:20 PM.
Sunrise & Sunset with Twilight in September
The chance that a given day will be muggy in San José is increasing during September, rising from 47% to 55% over the course of the month.
For reference, on June 2, the muggiest day of the year, there are muggy conditions 58% of the time, while on January 24, the least muggy day of the year, there are muggy conditions 3% of the time.
Humidity Comfort Levels in September
The average hourly wind speed in San José is essentially constant during September, remaining around 1.0 miles per hour throughout.
For reference, on February 5, the windiest day of the year, the daily average wind speed is 1.9 miles per hour, while on June 9, the calmest day of the year, the daily average wind speed is 1.0 miles per hour.
The lowest daily average wind speed during September is 1.0 miles per hour on September 11.
Average Wind Speed in September
Wind Direction in September
San José is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average surface water temperature in San José is essentially constant during September, remaining around 83°F throughout.
Average Water Temperature in September
The average daily incident shortwave solar energy in San José is essentially constant during September, remaining within 0.1 kWh of 3.9 kWh throughout.
Average Daily Incident Shortwave Solar Energy in September
For the purposes of this report, the geographical coordinates of San José are 9.933 deg latitude, -84.083 deg longitude, and 3,757 ft elevation.
The topography within 2 miles of San José contains only modest variations in elevation, with a maximum elevation change of 466 feet and an average elevation above sea level of 3,759 feet. Within 10 miles contains only modest variations in elevation (5,571 feet). Within 50 miles also contains extreme variations in elevation (12,303 feet).
The area within 2 miles of San José is covered by grassland (53%), trees (37%), and artificial surfaces (10%), within 10 miles by grassland (42%) and trees (42%), and within 50 miles by trees (53%) and grassland (17%).
This report illustrates the typical weather in San José year round, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There is only a single weather station, Juan Santamaría International Airport, in our network suitable to be used as a proxy for the historical temperature and dew point records of San José.
At a distance of 15 kilometers from San José, closer than our threshold of 150 kilometers, this station is deemed sufficiently nearby to be relied upon as our primary source for temperature and dew point records.
The station records are corrected for the elevation difference between the station and San José according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
Please note that the station records themselves may additionally have been back-filled using other nearby stations or the MERRA-2 reanalysis.
Time zones for aiports and weather stations are provided by AskGeo.com .