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January Weather in Greenwich Connecticut, United States

Daily high temperatures decrease by 2°F, from 40°F to 38°F, rarely falling below 24°F or exceeding 53°F. The lowest daily average high temperature is 37°F on January 23.

Daily low temperatures decrease by 3°F, from 27°F to 24°F, rarely falling below 10°F or exceeding 40°F. The lowest daily average low temperature is 24°F on January 29.

For reference, on July 20, the hottest day of the year, temperatures in Greenwich typically range from 68°F to 84°F, while on January 29, the coldest day of the year, they range from 24°F to 37°F.

Average High and Low Temperature in January in Greenwich

Average High and Low Temperature in January in GreenwichJan112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313110°F10°F15°F15°F20°F20°F25°F25°F30°F30°F35°F35°F40°F40°F45°F45°F50°F50°F55°F55°F60°F60°FDecFebJan 2337°FJan 2337°F25°F25°FJan 140°FJan 140°F27°F27°FJan 3138°FJan 3138°F24°F24°FJan 1138°FJan 1138°F26°F26°F
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 hourly average temperatures for the quarter of the year centered on January. 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.

Average Hourly Temperature in January in Greenwich

Average Hourly Temperature in January in GreenwichJan112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMDecFebfreezingfreezingvery coldvery cold
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.

Constanţa, Romania (4,840 miles away); Karabudakhkent, Russia (5,596 miles); and Nagano, Japan (6,712 miles) are the far-away foreign places with temperatures most similar to Greenwich (view comparison).

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The month of January in Greenwich experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 52% throughout the month.

The clearest day of the month is January 31, with clear, mostly clear, or partly cloudy conditions 49% of the time.

For reference, on February 28, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 53%, while on September 22, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 64%.

Cloud Cover Categories in January in Greenwich

Cloud Cover Categories in January in GreenwichJan11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%DecFebJan 148%Jan 148%Jan 3149%Jan 3149%Jan 1148%Jan 1148%Jan 2148%Jan 2148%clearmostly clearpartly cloudymostly cloudyovercast
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.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Greenwich, the chance of a wet day over the course of January is gradually decreasing, starting the month at 24% and ending it at 22%.

For reference, the year's highest daily chance of a wet day is 36% on August 2, and its lowest chance is 22% on January 29.

Over the course of January in Greenwich, the chance of a day with only rain decreases from 16% to 12%, the chance of a day with mixed snow and rain remains an essentially constant 5% throughout, and the chance of a day with only snow remains an essentially constant 5% throughout.

Probability of Precipitation in January in Greenwich

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 month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during January in Greenwich is gradually decreasing, starting the month at 2.4 inches, when it rarely exceeds 4.2 inches or falls below 0.7 inches, and ending the month at 2.0 inches, when it rarely exceeds 3.9 inches or falls below 0.6 inches.

Average Monthly Rainfall in January in Greenwich

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 snowfall.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day snowfall during January in Greenwich is increasing, starting the month at 6.1 inches, when it rarely exceeds 15.9 inches or falls below 0.5 inches, and ending the month at 7.5 inches, when it rarely exceeds 19.3 inches or falls below 0.3 inches.

The highest average 31-day accumulation is 7.5 inches on January 26.

Average Monthly Snowfall in January in Greenwich

The average snowfall (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 rainfall.

Over the course of January in Greenwich, the length of the day is increasing. From the start to the end of the month, the length of the day increases by 46 minutes, implying an average daily increase of 1 minute, 32 seconds, and weekly increase of 10 minutes, 46 seconds.

The shortest day of the month is January 1, with 9 hours, 17 minutes of daylight and the longest day is January 31, with 10 hours, 3 minutes of daylight.

Hours of Daylight and Twilight in January in Greenwich

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 latest sunrise of the month in Greenwich is 7:19 AM on January 4 and the earliest sunrise is 13 minutes earlier at 7:06 AM on January 31.

The earliest sunset is 4:36 PM on January 1 and the latest sunset is 33 minutes later at 5:09 PM on January 31.

Daylight saving time is observed in Greenwich during 2024, but it neither starts nor ends during January, so the entire month is in standard time.

For reference, on June 20, the longest day of the year, the Sun rises at 5:22 AM and sets 15 hours, 8 minutes later, at 8:30 PM, while on December 21, the shortest day of the year, it rises at 7:16 AM and sets 9 hours, 13 minutes later, at 4:29 PM.

Sunrise & Sunset with Twilight in January in Greenwich

The solar day over the course of January. 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 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.

Solar Elevation and Azimuth in January in Greenwich

Solar Elevation and Azimuth in January in GreenwichJan112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMDecFeb001010202020300001010202030
northeastsouthwest
Solar elevation and azimuth over the course of January 2024. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

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

Moon Rise, Set & Phases in January in Greenwich

Moon Rise, Set & Phases in January in GreenwichJan112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMDecFebDec 126:33 PMDec 126:33 PMDec 267:34 PMDec 267:34 PMJan 116:58 AMJan 116:58 AMJan 2512:55 PMJan 2512:55 PMFeb 96:00 PMFeb 96:00 PMFeb 247:31 AMFeb 247:31 AM7:01 AM7:01 AM3:54 PM3:54 PM3:56 PM3:56 PM8:13 AM8:13 AM7:51 AM7:51 AM4:51 PM4:51 PM4:52 PM4:52 PM8:04 AM8:04 AM7:07 AM7:07 AM5:03 PM5:03 PM4:51 PM4:51 PM6:57 AM6:57 AM
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.
Jan 2024IlluminationMoonriseMoonsetMoonriseMeridian PassingDistance
1
75%-10:48 AMWNW10:11 PME4:02 AMS251,574 mi
2
66%-11:07 AMW11:11 PME4:42 AMS251,383 mi
3
50%-11:26 AMW-5:20 AMS250,372 mi
4
47%12:11 AME11:45 AMW-5:59 AMS248,537 mi
5
37%1:13 AMESE12:07 PMWSW-6:41 AMS245,943 mi
6
28%2:18 AMESE12:32 PMWSW-7:25 AMS242,727 mi
7
19%3:27 AMESE1:02 PMWSW-8:15 AMS239,101 mi
8
11%4:38 AMSE1:42 PMSW-9:10 AMS235,344 mi
9
5%5:49 AMSE2:33 PMSW-10:11 AMS231,781 mi
10
1%6:55 AMSE3:36 PMSW-11:16 AMS228,747 mi
11
0%7:51 AMSE4:51 PMSW-12:21 PMS226,532 mi
12
2%8:37 AMESE6:11 PMWSW-1:24 PMS225,321 mi
13
7%9:13 AMESE7:32 PMWSW-2:22 PMS225,164 mi
14
15%9:43 AMESE8:50 PMWSW-3:16 PMS225,977 mi
15
25%10:08 AME10:06 PMW-4:05 PMS227,582 mi
16
36%10:32 AME11:19 PMW-4:53 PMS229,751 mi
17
50%10:55 AME--5:40 PMS232,255 mi
18
59%-12:32 AMWNW11:20 AMENE6:27 PMS234,893 mi
19
70%-1:44 AMWNW11:48 AMENE7:17 PMS237,519 mi
20
79%-2:56 AMWNW12:21 PMENE8:09 PMS240,036 mi
21
87%-4:05 AMNW1:01 PMNE9:03 PMS242,395 mi
22
93%-5:10 AMNW1:49 PMNE9:58 PMS244,573 mi
23
98%-6:07 AMNW2:46 PMNE10:53 PMS246,557 mi
24
100%-6:55 AMNW3:48 PMNE11:44 PMS248,326 mi
25
100%-7:33 AMWNW4:52 PMENE--
26
100%-8:04 AMWNW5:57 PMENE12:33 AMS249,842 mi
27
98%-8:30 AMWNW7:00 PMENE1:17 AMS251,041 mi
28
94%-8:52 AMWNW8:01 PMENE1:59 AMS251,840 mi
29
89%-9:12 AMW9:01 PME2:39 AMS252,139 mi
30
82%-9:30 AMW10:00 PME3:17 AMS251,838 mi
31
74%-9:49 AMW11:01 PMESE3:56 AMS250,853 mi

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 chance that a given day will be muggy in Greenwich is essentially constant during January, remaining around 0% throughout.

For reference, on August 1, the muggiest day of the year, there are muggy conditions 50% of the time, while on November 20, the least muggy day of the year, there are muggy conditions 0% of the time.

Humidity Comfort Levels in January in Greenwich

Humidity Comfort Levels in January in GreenwichJan11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%DecFebJan 10%Jan 10%Jan 310%Jan 310%Jan 110%Jan 110%Jan 210%Jan 210%drydry
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.

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 Greenwich is essentially constant during January, remaining within 0.2 miles per hour of 9.0 miles per hour throughout.

For reference, on February 26, the windiest day of the year, the daily average wind speed is 9.4 miles per hour, while on July 31, the calmest day of the year, the daily average wind speed is 5.6 miles per hour.

Average Wind Speed in January in Greenwich

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The hourly average wind direction in Greenwich throughout January is predominantly from the west, with a peak proportion of 46% on January 5.

Wind Direction in January in Greenwich

Wind Direction in January in GreenwichJan11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%20%80%40%60%60%40%80%20%100%0%DecFebwestnorthsoutheast
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).

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 surface water temperature in Greenwich is decreasing during January, falling by 5°F, from 44°F to 39°F, over the course of the month.

Average Water Temperature in January in Greenwich

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

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 Greenwich typically lasts for 7.2 months (220 days), from around April 2 to around November 8, rarely starting before March 16 or after April 20, and rarely ending before October 25 or after November 23.

The month of January in Greenwich is reliably fully outside of the growing season.

Time Spent in Various Temperature Bands and the Growing Season in January in Greenwich

Time Spent in Various Temperature Bands and the Growing Season in January in GreenwichJan11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%DecFeb0%Jan 160%Jan 16freezingvery coldcoldfrigidcool
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.

The average accumulated growing degree days in Greenwich are essentially constant during January, remaining within 2°F of 2°F throughout.

Growing Degree Days in January in Greenwich

The average growing degree days accumulated over the course of January, with 25th to 75th and 10th to 90th percentile bands.

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 in Greenwich is gradually increasing during January, rising by 0.7 kWh, from 1.8 kWh to 2.4 kWh, over the course of the month.

Average Daily Incident Shortwave Solar Energy in January in Greenwich

Average Daily Incident Shortwave Solar Energy in January in GreenwichJan11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310.0 kWh0.0 kWh0.5 kWh0.5 kWh1.0 kWh1.0 kWh1.5 kWh1.5 kWh2.0 kWh2.0 kWh2.5 kWh2.5 kWh3.0 kWh3.0 kWh3.5 kWh3.5 kWh4.0 kWh4.0 kWh4.5 kWh4.5 kWh5.0 kWh5.0 kWhDecFebJan 11.8 kWhJan 11.8 kWhJan 312.4 kWhJan 312.4 kWhJan 111.9 kWhJan 111.9 kWhJan 212.1 kWhJan 212.1 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.

For the purposes of this report, the geographical coordinates of Greenwich are 41.026 deg latitude, -73.628 deg longitude, and 92 ft elevation.

The topography within 2 miles of Greenwich contains only modest variations in elevation, with a maximum elevation change of 243 feet and an average elevation above sea level of 77 feet. Within 10 miles contains only modest variations in elevation (715 feet). Within 50 miles contains significant variations in elevation (1,657 feet).

The area within 2 miles of Greenwich is covered by artificial surfaces (59%), water (20%), and trees (18%), within 10 miles by water (37%) and trees (32%), and within 50 miles by trees (36%) and water (31%).

This report illustrates the typical weather in 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 Greenwich.

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

The stations contributing to this reconstruction are:

To get a sense of how much these sources agree with each other, you can view a comparison of Greenwich and the stations that contribute to our estimates of its temperature history and climate. Please note that each source's contribution is adjusted for elevation and the relative change present in the MERRA-2 data.

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 © OpenStreetMap contributors.

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.

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