Average Weather in September in San Sebastián Puerto Rico
Daily high temperatures are around 87°F, rarely falling below 84°F or exceeding 89°F.
Daily low temperatures are around 73°F, rarely falling below 71°F or exceeding 76°F.
For reference, on August 18, the hottest day of the year, temperatures in San Sebastián typically range from 74°F to 87°F, while on January 30, the coldest day of the year, they range from 68°F to 82°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 Sebastián experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 69% throughout the month. The highest chance of overcast or mostly cloudy conditions is 71% on September 27.
The clearest day of the month is September 1, with clear, mostly clear, or partly cloudy conditions 34% of the time.
For reference, on May 29, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 74%, while on January 10, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 82%.
Cloud Cover Categories in September
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In San Sebastián, the chance of a wet day over the course of September is essentially constant, remaining around 44% throughout.
For reference, the year's highest daily chance of a wet day is 45% on November 2, and its lowest chance is 15% on March 10.
Probability of Precipitation in September
The average sliding 31-day rainfall during September in San Sebastián is gradually increasing, starting the month at 3.3 inches, when it rarely exceeds 6.7 inches or falls below 1.1 inches, and ending the month at 3.7 inches, when it rarely exceeds 7.5 inches or falls below 0.9 inches.
The highest average 31-day accumulation is 3.8 inches on September 20.
Average Monthly Rainfall in September
Over the course of September in San Sebastián, the length of the day is gradually decreasing. From the start to the end of the month, the length of the day decreases by 30 minutes, implying an average daily decrease of 1 minute, 1 second, and weekly decrease of 7 minutes, 9 seconds.
The shortest day of the month is September 30, with 11 hours, 59 minutes of daylight and the longest day is September 1, with 12 hours, 28 minutes of daylight.
Hours of Daylight and Twilight in September
The earliest sunrise of the month in San Sebastián is 6:13 AM on September 1 and the latest sunrise is 5 minutes later at 6:18 AM on September 30.
The latest sunset is 6:41 PM on September 1 and the earliest sunset is 25 minutes earlier at 6:17 PM on September 30.
Daylight saving time is not observed in San Sebastián during 2021.
For reference, on June 21, the longest day of the year, the Sun rises at 5:52 AM and sets 13 hours, 14 minutes later, at 7:06 PM, while on December 21, the shortest day of the year, it rises at 6:55 AM and sets 11 hours, 2 minutes later, at 5:57 PM.
Sunrise & Sunset with Twilight in September
The figure below presents a compact representation of key lunar data for September 2021. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.
Moon Rise, Set & Phases in September
The chance that a given day will be muggy in San Sebastián is essentially constant during September, remaining around 100% throughout.
For reference, on July 11, the muggiest day of the year, there are muggy conditions 100% of the time, while on February 27, the least muggy day of the year, there are muggy conditions 75% of the time.
Humidity Comfort Levels in September
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in San Sebastián is decreasing during September, decreasing from 10.4 miles per hour to 9.2 miles per hour over the course of the month.
For reference, on July 14, the windiest day of the year, the daily average wind speed is 12.0 miles per hour, while on October 10, the calmest day of the year, the daily average wind speed is 8.9 miles per hour.
Average Wind Speed in September
The hourly average wind direction in San Sebastián throughout September is predominantly from the east, with a peak proportion of 88% on September 1.
Wind Direction in September
San Sebastián 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 Sebastián is essentially constant during September, remaining around 84°F throughout.
The highest average surface water temperature during September is 84°F on September 27.
Average Water Temperature in September
Temperatures in San Sebastián are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.
Time Spent in Various Temperature Bands and the Growing Season in September
The average accumulated growing degree days in San Sebastián are rapidly increasing during September, increasing by 850°F, from 6,581°F to 7,430°F, over the course of the month.
Growing Degree Days in September
The average daily incident shortwave solar energy in San Sebastián is gradually decreasing during September, falling by 0.6 kWh, from 5.2 kWh to 4.7 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in September
For the purposes of this report, the geographical coordinates of San Sebastián are 18.337 deg latitude, -66.990 deg longitude, and 272 ft elevation.
The topography within 2 miles of San Sebastián contains very significant variations in elevation, with a maximum elevation change of 843 feet and an average elevation above sea level of 407 feet. Within 10 miles contains very significant variations in elevation (2,103 feet). Within 50 miles contains large variations in elevation (4,442 feet).
The area within 2 miles of San Sebastián is covered by trees (30%), grassland (27%), cropland (25%), and shrubs (17%), within 10 miles by trees (53%) and cropland (20%), and within 50 miles by water (77%) and trees (12%).
This report illustrates the typical weather in San Sebastián, 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 are 2 weather stations near enough to contribute to our estimation of the temperature and dew point in San Sebastián.
For each station, the records are corrected for the elevation difference between that station and San Sebastián according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at San Sebastián is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between San Sebastián and a given station.
Time zones for airports and weather stations are provided by AskGeo.com .