Spring Weather in French Guiana French GuianaDaily high temperatures are around 84°F, rarely falling below 81°F or exceeding 88°F. Daily low temperatures are around 74°F, rarely falling below 72°F or exceeding 77°F. The highest daily average low temperature is 75°F on April 17. For reference, on October 1, the hottest day of the year, temperatures in French Guiana typically range from 72°F to 89°F, while on September 10, the coldest day of the year, they range from 72°F to 89°F. The figure below shows you a compact characterization of the hourly average spring temperatures. 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. CloudsThe spring in French Guiana experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 73% throughout the season. The highest chance of overcast or mostly cloudy conditions is 76% on May 6. The clearest day of the spring is March 24, with clear, mostly clear, or partly cloudy conditions 30% of the time. For reference, on May 4, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 76%, while on August 13, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 58%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In French Guiana, the chance of a wet day over the course of the spring is very rapidly increasing, starting the season at 64% and ending it at 93%. For reference, the year's highest daily chance of a wet day is 93% on May 31, and its lowest chance is 23% on September 25. RainfallTo show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day. The average sliding 31-day rainfall during the spring in French Guiana is very rapidly increasing, starting the season at 9.8 inches, when it rarely exceeds 16.7 inches or falls below 3.7 inches, and ending the season at 15.9 inches, when it rarely exceeds 22.3 inches or falls below 9.5 inches. The highest average 31-day accumulation is 17.4 inches on May 16. SunOver the course of the spring in French Guiana, the length of the day is gradually increasing. From the start to the end of the season, the length of the day increases by 18 minutes, implying an average daily increase of 12 seconds, and weekly increase of 1 minute, 22 seconds. The shortest day of the spring is March 1, with 12 hours, 3 minutes of daylight and the longest day is May 31, with 12 hours, 20 minutes of daylight. The latest sunrise of the spring in French Guiana is 6:42 AM on March 1 and the earliest sunrise is 24 minutes earlier at 6:19 AM on May 21. The latest sunset is 6:45 PM on March 1 and the earliest sunset is 9 minutes earlier at 6:36 PM on May 2. Daylight saving time is not observed in French Guiana during 2024. For reference, on June 20, the longest day of the year, the Sun rises at 6:23 AM and sets 12 hours, 21 minutes later, at 6:44 PM, while on December 21, the shortest day of the year, it rises at 6:33 AM and sets 11 hours, 54 minutes later, at 6:27 PM. The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation. MoonThe figure below presents a compact representation of key lunar data for the spring of 2024. 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. HumidityWe 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 chance that a given day will be muggy in French Guiana is essentially constant during the spring, remaining around 100% throughout. For reference, on January 1, the muggiest day of the year, there are muggy conditions 100% of the time, while on March 14, the least muggy day of the year, there are muggy conditions 100% of the time. WindThis 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 French Guiana is decreasing during the spring, decreasing from 7.3 miles per hour to 5.6 miles per hour over the course of the season. For reference, on February 18, the windiest day of the year, the daily average wind speed is 7.4 miles per hour, while on July 14, the calmest day of the year, the daily average wind speed is 4.8 miles per hour. The hourly average wind direction in French Guiana throughout the spring is predominantly from the east, with a peak proportion of 96% on May 19. Water TemperatureFrench Guiana 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 French Guiana is essentially constant during the spring, remaining within 1°F of 81°F throughout. Growing SeasonDefinitions 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 French Guiana 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. 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. The average accumulated growing degree days in French Guiana are very rapidly increasing during the spring, increasing by 2,625°F, from 1,691°F to 4,316°F, over the course of the season. Solar EnergyThis 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 in French Guiana is decreasing during the spring, falling by 1.1 kWh, from 5.7 kWh to 4.6 kWh, over the course of the season. The highest average daily incident shortwave solar energy during the spring is 5.9 kWh on March 25. The lowest average daily incident shortwave solar energy during the spring is 4.6 kWh on May 31. TopographyFor the purposes of this report, the geographical coordinates of French Guiana are 4.000 deg latitude, -53.000 deg longitude, and 0 ft elevation. The topography within 2 miles of French Guiana is essentially flat, with a maximum elevation change of 0 feet and an average elevation above sea level of 0 feet. Within 10 miles is also essentially flat (0 feet). Within 50 miles is also essentially flat (0 feet). The area within 2 miles of French Guiana is covered by trees (100%), within 10 miles by trees (99%), and within 50 miles by trees (97%). Data SourcesThis report illustrates the typical weather in French Guiana, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. The details of the data sources used for this report can be found on the Cayenne-Rochambeau page. DisclaimerThe 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. 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