1. WeatherSpark.com
  2. Costa Rica
  3. San José

Average Weather in San Isidro Costa Rica

The climate in San Isidro is warm, muggy, and overcast. Over the course of the year, the temperature typically varies from 69°F to 85°F and is rarely below 66°F or above 87°F.

Based on the tourism score, the best time of year to visit San Isidro for warm-weather activities is from mid December to mid March.

Climate Summary

warmJanFebMarAprMayJunJulAugSepOctNovDecNowNow60%60%4%4%overcastprecipitation: 7.0 inprecipitation: 7.0 in1.1 in1.1 inmuggy: 87%muggy: 87%11%11%tourism score: 7.1tourism score: 7.14.04.0
Click on each chart for more information.

Temperature

The temperature in San Isidro varies so little throughout the year that it is not entirely meaningful to discuss hot and cold seasons.

Average High and Low Temperature

Average High and Low Temperature in San IsidroJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F10°F10°F20°F20°F30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°F90°F90°F100°F100°FSep 2981°FSep 2981°FMar 2485°FMar 2485°F69°F69°F70°F70°FFeb 1984°FFeb 1984°FDec 1481°FDec 1481°F69°F69°F70°F70°F70°F70°FNowNow
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature

Average Hourly Temperature in San IsidroJanFebMarAprMayJunJulAugSepOctNovDec12 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMNowNowcomfortablecomfortablewarm
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Yaoundé, Cameroon (6,537 miles away); Salatiga, Indonesia (11,469 miles); and Claveria, Philippines (10,121 miles) are the far-away foreign places with temperatures most similar to San Isidro (view comparison).

Clouds

In San Isidro, the average percentage of the sky covered by clouds experiences extreme seasonal variation over the course of the year.

The clearer part of the year in San Isidro begins around November 26 and lasts for 4.4 months, ending around April 7. On January 2, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 60% of the time, and overcast or mostly cloudy 40% of the time.

The cloudier part of the year begins around April 7 and lasts for 7.6 months, ending around November 26. On May 28, the cloudiest day of the year, the sky is overcast or mostly cloudy 96% of the time, and clear, mostly clear, or partly cloudy 4% of the time.

Cloud Cover Categories

Cloud Cover Categories in San IsidroclearerclearercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Jan 260%Jan 260%May 284%May 284%Nov 2631%Nov 2631%Apr 732%Apr 732%NowNowclearmostly clearmostly cloudyovercastpartly cloudy
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in San Isidro varies significantly throughout the year.

The wetter season lasts 7.3 months, from April 28 to December 6, with a greater than 32% chance of a given day being a wet day. The chance of a wet day peaks at 52% on September 16.

The drier season lasts 4.7 months, from December 6 to April 28. The smallest chance of a wet day is 11% on March 13.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 52% on September 16.

Daily Chance of Precipitation

Daily Chance of Precipitation in San IsidrowetdrydryJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Sep 1652%Sep 1652%Mar 1311%Mar 1311%Jan 119%Jan 119%Apr 2832%Apr 2832%NowNowrain
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. San Isidro experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year in San Isidro. The most rain falls during the 31 days centered around October 15, with an average total accumulation of 7.0 inches.

The least rain falls around March 15, with an average total accumulation of 1.1 inches.

Average Monthly Rainfall

Average Monthly Rainfall in San IsidroJanFebMarAprMayJunJulAugSepOctNovDec0 in0 in2 in2 in4 in4 in6 in6 in8 in8 in10 in10 in12 in12 in14 in14 inOct 157.0 inOct 157.0 inMar 151.1 inMar 151.1 inJun 56.7 inJun 56.7 inJul 306.3 inJul 306.3 inNowNow
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Sun

The length of the day in San Isidro does not vary substantially over the course of the year, staying within 40 minutes of 12 hours throughout. In 2021, the shortest day is December 21, with 11 hours, 35 minutes of daylight; the longest day is June 20, with 12 hours, 40 minutes of daylight.

Hours of Daylight and Twilight

Hours of Daylight and Twilight in San IsidroJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 6 minMar 2012 hr, 6 minMar 2012 hr, 40 minJun 2012 hr, 40 minJun 2012 hr, 7 minSep 2212 hr, 7 minSep 2211 hr, 35 minDec 2111 hr, 35 minDec 21nightnightdayNowNow
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise is at 5:13 AM on May 29, and the latest sunrise is 43 minutes later at 5:56 AM on January 27. The earliest sunset is at 5:10 PM on November 14, and the latest sunset is 49 minutes later at 5:59 PM on July 13.

Daylight saving time (DST) is not observed in San Isidro during 2021.

Sunrise & Sunset with Twilight

Sunrise & Sunset with Twilight in San IsidroJanFebMarAprMayJunJulAugSepOctNovDec12 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PMMay 295:13 AMMay 295:13 AM5:59 PMJul 135:59 PMJul 13Nov 145:10 PMNov 145:10 PM5:56 AMJan 275:56 AMJan 27daynightnightSolarMidnightSolarMidnightSolarNoonSunriseSunsetNowNow
The solar day over the course of the year 2021. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

Moon

The figure below presents a compact representation of key lunar data for 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.

Moon Rise, Set & Phases

The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.

Humidity

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

San Isidro experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 8.8 months, from March 24 to December 16, during which time the comfort level is muggy, oppressive, or miserable at least 30% of the time. The muggiest day of the year is June 3, with muggy conditions 87% of the time.

The least muggy day of the year is January 25, with muggy conditions 11% of the time.

Humidity Comfort Levels

Humidity Comfort Levels in San IsidromuggyJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Jan 2511%Jan 2511%87%Jun 387%Jun 3Mar 2430%Mar 2430%Dec 1630%Dec 1630%NowNowoppressiveoppressivemuggymuggyhumidhumidcomfortablecomfortabledrydry
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

Wind

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in San Isidro experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 2.2 months, from August 30 to November 6, with average wind speeds of more than 2.6 miles per hour. The windiest day of the year is October 8, with an average hourly wind speed of 3.3 miles per hour.

The calmer time of year lasts for 9.7 months, from November 6 to August 30. The calmest day of the year is December 10, with an average hourly wind speed of 1.9 miles per hour.

Average Wind Speed

Average Wind Speed in San IsidrowindyJanFebMarAprMayJunJulAugSepOctNovDec0.0 mph0.0 mph0.5 mph0.5 mph1.0 mph1.0 mph1.5 mph1.5 mph2.0 mph2.0 mph2.5 mph2.5 mph3.0 mph3.0 mph3.5 mph3.5 mph4.0 mph4.0 mph4.5 mph4.5 mph5.0 mph5.0 mph5.5 mph5.5 mphOct 83.3 mphOct 83.3 mphDec 101.9 mphDec 101.9 mphAug 302.6 mphAug 302.6 mphNowNow
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The predominant average hourly wind direction in San Isidro varies throughout the year.

The wind is most often from the west for 7.7 months, from April 16 to December 6, with a peak percentage of 69% on October 1. The wind is most often from the north for 4.3 months, from December 6 to April 16, with a peak percentage of 50% on January 1.

Wind Direction

Wind Direction in San IsidroNWNJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%NowNowwestnorthsoutheast
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

San Isidro 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 water temperature does not vary significantly over the course of the year, remaining within 1°F of 83°F throughout.

Average Water Temperature

Average Water Temperature in San IsidroJanFebMarAprMayJunJulAugSepOctNovDec80°F80°F81°F81°F82°F82°F83°F83°F84°F84°F85°F85°F86°F86°FApr 685°FApr 685°F82°FNov 1082°FNov 10Feb 2484°FFeb 2484°FMay 1884°FMay 1884°FOct 1182°FOct 1182°FDec 1482°FDec 1482°FNowNow
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Best Time of Year to Visit

To characterize how pleasant the weather is in San Isidro throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit San Isidro for general outdoor tourist activities is from mid December to mid March, with a peak score in the second week of January.

Tourism Score

Tourism Score in San Isidrobest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810107.17.14.04.04.14.1NowNowprecipitationprecipitationcloudscloudstemperaturetemperature tourism score
The tourism score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit San Isidro for hot-weather activities is from mid December to late March, with a peak score in the first week of January.

Beach/Pool Score

Beach/Pool Score in San Isidrobest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810106.76.73.83.84.04.0NowNowprecipitationprecipitationcloudscloudstemperaturetemperature beach/pool score
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Growing Season

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

Temperatures in San Isidro 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

Time Spent in Various Temperature Bands and the Growing Season in San IsidroJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%100%Jan 1100%Jan 1100%Jul 3100%Jul 3NowNowcomfortablewarmhot
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Growing Degree Days

Growing Degree Days in San IsidroJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F1,000°F1,000°F2,000°F2,000°F3,000°F3,000°F4,000°F4,000°F5,000°F5,000°F6,000°F6,000°F7,000°F7,000°F8,000°F8,000°F9,000°F9,000°FJan 590°FJan 590°FMar 141,800°FMar 141,800°FDec 318,856°FDec 318,856°FNowNow
The average growing degree days accumulated over the course of the year, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences significant seasonal variation over the course of the year.

The brighter period of the year lasts for 2.7 months, from January 21 to April 12, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest day of the year is March 16, with an average of 6.6 kWh.

The darker period of the year lasts for 6.0 months, from May 18 to November 16, with an average daily incident shortwave energy per square meter below 4.0 kWh. The darkest day of the year is October 10, with an average of 3.4 kWh.

Average Daily Incident Shortwave Solar Energy

Average Daily Incident Shortwave Solar Energy in San IsidrobrightdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWhMar 166.6 kWhMar 166.6 kWhOct 103.4 kWhOct 103.4 kWhJan 215.9 kWhJan 215.9 kWhMay 184.0 kWhMay 184.0 kWhNov 164.0 kWhNov 164.0 kWhNowNow
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

For the purposes of this report, the geographical coordinates of San Isidro are 9.372 deg latitude, -83.704 deg longitude, and 2,283 ft elevation.

The topography within 2 miles of San Isidro contains very significant variations in elevation, with a maximum elevation change of 830 feet and an average elevation above sea level of 2,396 feet. Within 10 miles contains very significant variations in elevation (7,838 feet). Within 50 miles also contains extreme variations in elevation (12,520 feet).

The area within 2 miles of San Isidro is covered by grassland (54%), trees (21%), cropland (13%), and shrubs (12%), within 10 miles by trees (45%) and grassland (27%), and within 50 miles by trees (45%) and water (32%).

Data Sources

This report illustrates the typical weather in San Isidro, 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 Isidro.

For each station, the records are corrected for the elevation difference between that station and San Isidro 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 Isidro is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between San Isidro and a given station.

The stations contributing to this reconstruction are: Juan Santamaría International Airport (75%, 89 kilometers, northwest) and David Airport (25%, 177 kilometers, southeast).

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for airports and weather stations are provided by AskGeo.com .

Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.