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Average Weather in St. Marys Georgia, United States

In St. Marys, the summers are long, hot, oppressive, and mostly cloudy; the winters are short, cool, and partly cloudy; and it is wet year round. Over the course of the year, the temperature typically varies from 45°F to 91°F and is rarely below 31°F or above 96°F.

Based on the tourism score, the best times of year to visit St. Marys for warm-weather activities are from late March to mid May and from early October to mid November.

Climate Summary

coolcomfortablewarmhotwarmcomfortableJanFebMarAprMayJunJulAugSepOctNovDec66%66%39%39%clearovercastprecipitation: 5.1 inprecipitation: 5.1 in2.0 in2.0 inmuggy: 99%muggy: 99%2%2%drydrytourism score: 6.7tourism score: 6.73.53.5
Click on each chart for more information.

Temperature

The hot season lasts for 3.9 months, from May 25 to September 22, with an average daily high temperature above 86°F. The hottest day of the year is July 23, with an average high of 91°F and low of 75°F.

The cool season lasts for 3.0 months, from December 3 to March 2, with an average daily high temperature below 69°F. The coldest day of the year is January 17, with an average low of 45°F and high of 64°F.

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 St. MarysJanFebMarAprMayJunJulAugSepOctNovDec12 AM4 AM8 AM12 PM4 PM8 PM12 AMcoldcoldcoldcoolcoolwarmhotcomfortablecoldcomfortable
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.

Kafr ad Dawwār, Egypt (6,255 miles away) and Longmen, China (8,385 miles) are the far-away foreign places with temperatures most similar to St. Marys (view comparison).

Clouds

In St. Marys, 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 St. Marys begins around September 18 and lasts for 8.6 months, ending around June 6. On October 27, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 66% of the time, and overcast or mostly cloudy 34% of the time.

The cloudier part of the year begins around June 6 and lasts for 3.4 months, ending around September 18. On July 12, the cloudiest day of the year, the sky is overcast or mostly cloudy 61% of the time, and clear, mostly clear, or partly cloudy 39% of the time.

Cloud Cover Categories

Cloud Cover Categories in St. MarysclearerclearercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Oct 2766%Oct 2766%Jul 1239%Jul 1239%Sep 1852%Sep 1852%Jun 653%Jun 653%clearpartly cloudymostly cloudyovercastmostly clear
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 St. Marys varies significantly throughout the year.

The wetter season lasts 3.8 months, from June 1 to September 26, with a greater than 36% chance of a given day being a wet day. The chance of a wet day peaks at 55% on July 31.

The drier season lasts 8.2 months, from September 26 to June 1. The smallest chance of a wet day is 17% on October 31.

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 55% on July 31.

Daily Chance of Precipitation

Daily Chance of Precipitation in St. MaryswetdrydryJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Jul 3155%Jul 3155%Oct 3117%Oct 3117%Jan 122%Jan 122%Jun 136%Jun 136%Sep 2636%Sep 2636%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. St. Marys experiences significant seasonal variation in monthly rainfall.

Rain falls throughout the year in St. Marys. The most rain falls during the 31 days centered around August 31, with an average total accumulation of 5.1 inches.

The least rain falls around November 11, with an average total accumulation of 2.0 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 St. Marys varies significantly over the course of the year. In 2018, the shortest day is December 21, with 10 hours, 9 minutes of daylight; the longest day is June 21, with 14 hours, 8 minutes of daylight.

Hours of Daylight and Twilight

Hours of Daylight and Twilight in St. MarysJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 8 minMar 2012 hr, 8 minMar 2014 hr, 8 minJun 2114 hr, 8 minJun 2112 hr, 8 minSep 2212 hr, 8 minSep 2210 hr, 9 minDec 2110 hr, 9 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 6:22 AM on June 11, and the latest sunrise is 1 hour, 20 minutes later at 7:42 AM on November 3. The earliest sunset is at 5:24 PM on December 2, and the latest sunset is 3 hours, 9 minutes later at 8:33 PM on June 30.

Daylight saving time (DST) is observed in St. Marys during 2018, starting in the spring on March 11, lasting 7.8 months, and ending in the fall on November 4.

Sunrise & Sunset with Twilight and Daylight Saving Time

Sunrise & Sunset with Twilight and Daylight Saving Time in St. MarysJanFebMarAprMayJunJulAugSepOctNovDec2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 116:22 AMJun 116:22 AM8:33 PMJun 308:33 PMJun 30Dec 25:24 PMDec 25:24 PM7:42 AMNov 37:42 AMNov 3Mar 11DSTMar 11DSTDSTNov 4DSTNov 4daynightnightnightnightSolarMidnightSolarMidnightSolarNoonSunriseSunset
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. The transitions to and from daylight saving time are indicated by the 'DST' labels.

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.

St. Marys experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 6.8 months, from April 21 to November 14, during which time the comfort level is muggy, oppressive, or miserable at least 26% of the time. The muggiest day of the year is July 31, with muggy conditions 99% of the time.

The least muggy day of the year is February 3, with muggy conditions 2% of the time.

Humidity Comfort Levels

Humidity Comfort Levels in St. MarysmuggyJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Feb 32%Feb 32%99%Jul 3199%Jul 31Apr 2126%Apr 2126%Nov 1426%Nov 1426%miserablemiserableoppressiveoppressivedrydryhumidhumidmuggymuggy
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 St. Marys experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 8.2 months, from September 12 to May 19, with average wind speeds of more than 7.3 miles per hour. The windiest day of the year is January 29, with an average hourly wind speed of 8.4 miles per hour.

The calmer time of year lasts for 3.8 months, from May 19 to September 12. The calmest day of the year is August 5, with an average hourly wind speed of 6.2 miles per hour.

Average Wind Speed

Average Wind Speed in St. MaryswindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph2 mph4 mph6 mph8 mph10 mph12 mphJan 298.4 mphJan 298.4 mphAug 56.2 mphAug 56.2 mphMay 197.3 mphMay 197.3 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 St. Marys varies throughout the year.

The wind is most often from the south for 4.0 weeks, from March 29 to April 26 and for 2.2 months, from June 10 to August 16, with a peak percentage of 44% on July 19. The wind is most often from the east for 1.5 months, from April 26 to June 10 and for 2.1 months, from August 16 to October 19, with a peak percentage of 48% on September 8. The wind is most often from the north for 2.6 months, from October 19 to January 8, with a peak percentage of 33% on January 1.

Wind Direction

Wind Direction in St. MarysWSESENJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%westsoutheastnorth
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

St. Marys 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 significant seasonal variation over the course of the year.

The time of year with warmer water lasts for 4.0 months, from June 7 to October 8, with an average temperature above 79°F. The day of the year with the warmest water is August 20, with an average temperature of 83°F.

The time of year with cooler water lasts for 3.8 months, from December 15 to April 7, with an average temperature below 66°F. The day of the year with the coolest water is February 21, with an average temperature of 62°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 St. Marys 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 times of year to visit St. Marys for general outdoor tourist activities are from late March to mid May and from early October to mid November, with a peak score in the last week of April.

Tourism Score

Tourism Score in St. Marysbest timeJanFebMarAprMayJunJulAugSepOctNovDec02468106.76.73.53.56.66.6 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 times of year to visit St. Marys for hot-weather activities are from early May to mid June and from mid September to mid October, with a peak score in the third week of May.

Beach/Pool Score

Beach/Pool Score in St. MarysJanFebMarAprMayJunJulAugSepOctNovDec02468106.16.10.80.85.85.84.54.5 precipitationprecipitationcloudscloudstemperaturetemperaturebeach/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).

The growing season in St. Marys typically lasts for 10 months (311 days), from around February 12 to around December 20, rarely starting before January 16 or after March 14, and rarely ending before November 24 or after January 14.

Time Spent in Various Temperature Bands and the Growing Season

Time Spent in Various Temperature Bands and the Growing Season in St. Marysgrowing seasonJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%50%Feb 1250%Feb 1250%Dec 2050%Dec 2090%Mar 1490%Mar 1490%Nov 2490%Nov 2410%Jan 1610%Jan 16Jul 18100%Jul 18100%coldcoolcomfortablewarmhotvery cold
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.

Based on growing degree days alone, the first spring blooms in St. Marys should appear around January 15, only rarely appearing before January 9 or after January 27.

Growing Degree Days

Growing Degree Days in St. MarysJanFebMarAprMayJunJulAugSepOctNovDec0°F1,000°F2,000°F3,000°F4,000°F5,000°F6,000°F7,000°FJan 1590°FJan 1590°FApr 7900°FApr 7900°FMay 201,800°FMay 201,800°FDec 317,211°FDec 317,211°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 significant seasonal variation over the course of the year.

The brighter period of the year lasts for 2.3 months, from April 5 to June 16, with an average daily incident shortwave energy per square meter above 6.0 kWh. The brightest day of the year is May 14, with an average of 6.8 kWh.

The darker period of the year lasts for 2.8 months, from November 10 to February 4, with an average daily incident shortwave energy per square meter below 3.8 kWh. The darkest day of the year is December 21, with an average of 3.0 kWh.

Average Daily Incident Shortwave Solar Energy

Average Daily Incident Shortwave Solar Energy in St. MarysbrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh1 kWh2 kWh3 kWh4 kWh5 kWh6 kWh7 kWh8 kWh9 kWhMay 146.8 kWhMay 146.8 kWhDec 213.0 kWhDec 213.0 kWhFeb 43.8 kWhFeb 43.8 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 St. Marys are 30.731 deg latitude, -81.546 deg longitude, and 3 ft elevation.

The topography within 2 miles of St. Marys is essentially flat, with a maximum elevation change of 20 feet and an average elevation above sea level of 5 feet. Within 10 miles is also essentially flat (66 feet). Within 50 miles is essentially flat (197 feet).

The area within 2 miles of St. Marys is covered by herbaceous vegetation (50%), artificial surfaces (26%), and water (20%), within 10 miles by herbaceous vegetation (34%) and water (26%), and within 50 miles by water (41%) and trees (28%).

Data Sources

This report illustrates the typical weather in St. Marys, 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 3 weather stations near enough to contribute to our estimation of the temperature and dew point in St. Marys.

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

The stations contributing to this reconstruction are: Fernandina Beach Municipal Airport (82%, 15 kilometers, southeast); Malcolm Mc Kinnon Airport (13%, 49 kilometers, north); and Waycross-Ware County Airport (4.6%, 100 kilometers, northwest).

Other Data

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.

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 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.