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Average Weather in São Tomé São Tomé & Príncipe

The climate in São Tomé is warm, oppressive, and overcast. Over the course of the year, the temperature typically varies from 75°F to 82°F and is rarely below 73°F or above 84°F.

Climate Summary

warmJanFebMarAprMayJunJulAugSepOctNovDec36%36%11%11%overcastprecipitation: 5.4 inprecipitation: 5.4 in0.1 in0.1 inmuggy: 100%muggy: 100%99%99%tourism score: 6.9tourism score: 6.92.42.4
Click on each chart for more information.

Based on the tourism score, the best time of year to visit São Tomé for warm-weather activities is from mid June to late September.

Temperature

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

Average High and Low Temperature

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 São ToméJanFebMarAprMayJunJulAugSepOctNovDec12 AM4 AM8 AM12 PM4 PM8 PM12 AMwarm
The average hourly temperature, color coded into bands: 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 shaded overlays indicate night and civil twilight.

Tofol, Micronesia (10,766 miles away) is the far-away foreign place with temperatures most similar to São Tomé (view comparison).

Clouds

In São Tomé, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.

The clearer part of the year in São Tomé begins around May 26 and lasts for 6.0 months, ending around November 28. On June 29, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 36% of the time, and overcast or mostly cloudy 64% of the time.

The cloudier part of the year begins around November 28 and lasts for 6.0 months, ending around May 26. On March 23, the cloudiest day of the year, the sky is overcast or mostly cloudy 89% of the time, and clear, mostly clear, or partly cloudy 11% of the time.

Cloud Cover Categories

Cloud Cover Categories in São ToméclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Jun 2936%Jun 2936%Mar 2311%Mar 2311%May 2624%May 2624%Nov 2824%Nov 2824%mostly clearpartly cloudymostly cloudyovercastclear
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

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

The wetter season lasts 7.3 months, from October 17 to May 27, with a greater than 33% chance of a given day being a wet day. The chance of a wet day peaks at 64% on March 29.

The drier season lasts 4.7 months, from May 27 to October 17. The smallest chance of a wet day is 1% on August 15.

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 64% on March 29.

Daily Chance of Precipitation

Daily Chance of Precipitation in São ToméwetwetdryJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Mar 2964%Mar 2964%Aug 151%Aug 151%Jan 139%Jan 139%Oct 1733%Oct 1733%May 2733%May 2733%rain
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. São Tomé experiences extreme seasonal variation in monthly rainfall.

The rainy period of the year lasts for 9.0 months, from September 23 to June 23, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around April 4, with an average total accumulation of 5.4 inches.

The rainless period of the year lasts for 3.0 months, from June 23 to September 23. The least rain falls around August 13, with an average total accumulation of 0.1 inches.

Average Monthly Rainfall

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 São Tomé does not vary substantially over the course of the year, staying within 8 minutes of 12 hours throughout. In 2018, the shortest day is December 21, with 12 hours, 6 minutes of daylight; the longest day is June 21, with 12 hours, 9 minutes of daylight.

Hours of Daylight and Twilight

Hours of Daylight and Twilight in São ToméJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 7 minMar 2012 hr, 7 minMar 2012 hr, 9 minJun 2112 hr, 9 minJun 2112 hr, 7 minSep 2312 hr, 7 minSep 2312 hr, 6 minDec 2112 hr, 6 minDec 21nightnightday
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 November 3, and the latest sunrise is 31 minutes later at 5:44 AM on February 11. The earliest sunset is at 5:19 PM on November 3, and the latest sunset is 31 minutes later at 5:50 PM on February 11.

Daylight saving time (DST) is not observed in São Tomé during 2018.

Sunrise & Sunset with Twilight

Sunrise & Sunset with Twilight in São ToméJanFebMarAprMayJunJulAugSepOctNovDec12 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PMNov 35:13 AMNov 35:13 AM5:50 PMFeb 115:50 PMFeb 11Nov 35:19 PMNov 35:19 PM5:44 AMFeb 115:44 AMFeb 11daynightnightSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of the year 2018. 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.

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.

The perceived humidity level in São Tomé, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, staying within 1% of 99% throughout.

Humidity Comfort Levels

Humidity Comfort Levels in São ToméJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Aug 1199%Aug 1199%100%Apr 16100%Apr 16miserablemiserableoppressiveoppressivemuggymuggy
The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

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 São Tomé experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 5.9 months, from May 17 to November 13, with average wind speeds of more than 9.2 miles per hour. The windiest day of the year is June 17, with an average hourly wind speed of 10.6 miles per hour.

The calmer time of year lasts for 6.1 months, from November 13 to May 17. The calmest day of the year is January 1, with an average hourly wind speed of 7.8 miles per hour.

Average Wind Speed

Average Wind Speed in São ToméwindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph2 mph4 mph6 mph8 mph10 mph12 mphJun 1710.6 mphJun 1710.6 mphJan 17.8 mphJan 17.8 mphNov 139.2 mphNov 139.2 mph
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 São Tomé varies throughout the year.

The wind is most often from the south for 11 months, from January 29 to December 26, with a peak percentage of 93% on June 22. The wind is most often from the west for 1.1 months, from December 26 to January 29, with a peak percentage of 51% on January 1.

Wind Direction

Wind Direction in São ToméWSJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%westsouth
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 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

São Tomé 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 experiences some seasonal variation over the course of the year.

The time of year with warmer water lasts for 3.5 months, from January 25 to May 10, with an average temperature above 83°F. The day of the year with the warmest water is March 23, with an average temperature of 84°F.

The time of year with cooler water lasts for 3.0 months, from June 24 to September 25, with an average temperature below 79°F. The day of the year with the coolest water is August 8, with an average temperature of 77°F.

Average Water Temperature

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 São Tomé 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 São Tomé for general outdoor tourist activities is from mid June to late September, with a peak score in the third week of July.

Tourism Score

Tourism Score in São Tomébest timeJanFebMarAprMayJunJulAugSepOctNovDec02468106.96.92.42.4 precipitationprecipitationcloudscloudstemperaturetemperaturetourism 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 São Tomé for hot-weather activities is from late May to mid October, with a peak score in the last week of June.

Beach/Pool Score

Beach/Pool Score in São Tomébest timeJanFebMarAprMayJunJulAugSepOctNovDec02468106.96.94.74.76.86.8 precipitationprecipitationtemperaturetemperaturebeach/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 São Tomé 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 São ToméJanFebMarAprMayJunJulAugSepOctNovDec0%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 3comfortablewarm
The percentage of time spent in various temperature bands: 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 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 São ToméJanFebMarAprMayJunJulAugSepOctNovDec0°F2,000°F4,000°F6,000°F8,000°F10,000°FJan 490°FJan 490°FMar 11,800°FMar 11,800°FDec 3110,548°FDec 3110,548°F
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 some seasonal variation over the course of the year.

The brighter period of the year lasts for 2.1 months, from August 8 to October 10, with an average daily incident shortwave energy per square meter above 5.0 kWh. The brightest day of the year is September 6, with an average of 5.3 kWh.

The darker period of the year lasts for 2.4 months, from March 1 to May 14, with an average daily incident shortwave energy per square meter below 4.0 kWh. The darkest day of the year is April 11, with an average of 3.7 kWh.

Average Daily Incident Shortwave Solar Energy

Average Daily Incident Shortwave Solar Energy in São TomébrightdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh1 kWh2 kWh3 kWh4 kWh5 kWh6 kWh7 kWhSep 65.3 kWhSep 65.3 kWhApr 113.7 kWhApr 113.7 kWhOct 105.0 kWhOct 105.0 kWhMar 14.0 kWhMar 14.0 kWh
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 São Tomé are 0.337 deg latitude, 6.727 deg longitude, and 59 ft elevation.

The topography within 2 miles of São Tomé contains only modest variations in elevation, with a maximum elevation change of 404 feet and an average elevation above sea level of 95 feet. Within 10 miles contains only modest variations in elevation (4,662 feet). Within 50 miles also contains extreme variations in elevation (6,657 feet).

The area within 2 miles of São Tomé is covered by cropland (54%), water (24%), and trees (14%), within 10 miles by water (60%) and cropland (16%), and within 50 miles by water (97%).

Data Sources

This report illustrates the typical weather in São Tomé, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

São Tomé is further than 200 kilometers from the nearest reliable weather station, so the weather-related data on this page were taken entirely from NASA's MERRA-2 satellite-era reanalysis . 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.

The temperature and dew point estimates are corrected for the difference between the reference elevation of the MERRA-2 grid cell and the elevation of São Tomé, according to the International Standard Atmosphere .

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.

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 aiports 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.