Average Weather in Old Greenwich Connecticut, United States
In Old Greenwich, the summers are warm and humid, the winters are very cold, and it is wet and partly cloudy year round. Over the course of the year, the temperature typically varies from 24°F to 83°F and is rarely below 10°F or above 91°F.
Based on the tourism score, the best time of year to visit Old Greenwich for warm-weather activities is from mid June to late September.
The warm season lasts for 3.4 months, from June 2 to September 16, with an average daily high temperature above 74°F. The hottest day of the year is July 21, with an average high of 83°F and low of 68°F.
The cold season lasts for 3.3 months, from December 4 to March 13, with an average daily high temperature below 47°F. The coldest day of the year is January 29, with an average low of 24°F and high of 37°F.
Average High and Low Temperature
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
In Old Greenwich, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.
The clearer part of the year in Old Greenwich begins around June 26 and lasts for 4.6 months, ending around November 12. On September 23, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 64% of the time, and overcast or mostly cloudy 36% of the time.
The cloudier part of the year begins around November 12 and lasts for 7.4 months, ending around June 26. On February 28, the cloudiest day of the year, the sky is overcast or mostly cloudy 53% of the time, and clear, mostly clear, or partly cloudy 47% of the time.
Cloud Cover Categories
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. The chance of wet days in Old Greenwich varies throughout the year.
The wetter season lasts 8.3 months, from April 1 to December 11, with a greater than 29% chance of a given day being a wet day. The chance of a wet day peaks at 35% on May 30.
The drier season lasts 3.7 months, from December 11 to April 1. The smallest chance of a wet day is 22% on January 29.
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 35% on May 30.
Daily Chance of Precipitation
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. Old Greenwich experiences some seasonal variation in monthly rainfall.
Rain falls throughout the year in Old Greenwich. The most rain falls during the 31 days centered around June 4, with an average total accumulation of 3.8 inches.
The least rain falls around February 6, with an average total accumulation of 2.0 inches.
Average Monthly Rainfall
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Old Greenwich experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 4.5 months, from November 20 to April 5, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around January 26, with an average total liquid-equivalent accumulation of 0.7 inches.
The snowless period of the year lasts for 7.5 months, from April 5 to November 20. The least snow falls around July 25, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Old Greenwich varies significantly over the course of the year. In 2019, the shortest day is December 21, with 9 hours, 13 minutes of daylight; the longest day is June 21, with 15 hours, 8 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:21 AM on June 15, and the latest sunrise is 2 hours, 5 minutes later at 7:26 AM on November 2. The earliest sunset is at 4:25 PM on December 8, and the latest sunset is 4 hours, 5 minutes later at 8:30 PM on June 27.
Daylight saving time (DST) is observed in Old Greenwich during 2019, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.
Sunrise & Sunset with Twilight and Daylight Saving Time
Old Greenwich experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 3.6 months, from June 6 to September 25, during which time the comfort level is muggy, oppressive, or miserable at least 13% of the time. The muggiest day of the year is August 2, with muggy conditions 52% of the time.
The least muggy day of the year is February 23, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Old Greenwich experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 6.2 months, from October 18 to April 24, with average wind speeds of more than 7.7 miles per hour. The windiest day of the year is February 26, with an average hourly wind speed of 9.6 miles per hour.
The calmer time of year lasts for 5.8 months, from April 24 to October 18. The calmest day of the year is August 1, with an average hourly wind speed of 5.8 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Old Greenwich varies throughout the year.
The wind is most often from the north for 1.1 months, from March 9 to April 11, with a peak percentage of 34% on March 11. The wind is most often from the west for 3.3 weeks, from April 11 to May 4 and for 5.2 months, from October 2 to March 9, with a peak percentage of 30% on April 19. The wind is most often from the south for 4.9 months, from May 4 to October 2, with a peak percentage of 38% on July 28.
Old Greenwich 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 3.5 months, from June 24 to October 8, with an average temperature above 65°F. The day of the year with the warmest water is August 12, with an average temperature of 72°F.
The time of year with cooler water lasts for 3.5 months, from December 30 to April 15, with an average temperature below 44°F. The day of the year with the coolest water is February 21, with an average temperature of 37°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in Old Greenwich 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 Old Greenwich for general outdoor tourist activities is from mid June to late September, with a peak score in the first week of September.
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 Old Greenwich for hot-weather activities is from early July to late August, with a peak score in the last week of July.
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.
The growing season in Old Greenwich typically lasts for 7.0 months (215 days), from around April 5 to around November 6, rarely starting before March 20 or after April 22, and rarely ending before October 20 or after November 22.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Old Greenwich should appear around April 17, only rarely appearing before April 4 or after April 27.
Growing Degree Days
The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.
The brighter period of the year lasts for 3.7 months, from April 30 to August 21, with an average daily incident shortwave energy per square meter above 5.8 kWh. The brightest day of the year is June 30, with an average of 6.9 kWh.
The darker period of the year lasts for 3.2 months, from November 5 to February 10, with an average daily incident shortwave energy per square meter below 2.8 kWh. The darkest day of the year is December 23, with an average of 1.7 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Old Greenwich are 41.023 deg latitude, -73.565 deg longitude, and 3 ft elevation.
The topography within 2 miles of Old Greenwich contains only modest variations in elevation, with a maximum elevation change of 118 feet and an average elevation above sea level of 21 feet. Within 10 miles contains only modest variations in elevation (627 feet). Within 50 miles contains significant variations in elevation (1,654 feet).
The area within 2 miles of Old Greenwich is covered by water (51%) and artificial surfaces (41%), within 10 miles by water (45%) and trees (29%), and within 50 miles by trees (35%) and water (33%).
This report illustrates the typical weather in Old Greenwich, 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 4 weather stations near enough to contribute to our estimation of the temperature and dew point in Old Greenwich.
For each station, the records are corrected for the elevation difference between that station and Old Greenwich 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 Old Greenwich is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Old Greenwich and a given station.
The stations contributing to this reconstruction are: Westchester County Airport (52%, 13 kilometers, west); Republic Airport (19%, 34 kilometers, south); Danbury Municipal Airport (14%, 39 kilometers, north); and Igor I Sikorsky Memorial Airport (15%, 40 kilometers, northeast).
Time zones for aiports and weather stations are provided by AskGeo.com .