January Weather in Guidonia Montecelio ItalyDaily high temperatures are around 54°F, rarely falling below 47°F or exceeding 61°F. The lowest daily average high temperature is 54°F on January 11. Daily low temperatures are around 37°F, rarely falling below 28°F or exceeding 46°F. The lowest daily average low temperature is 36°F on January 19. For reference, on August 4, the hottest day of the year, temperatures in Guidonia Montecelio typically range from 66°F to 91°F, while on January 19, the coldest day of the year, they range from 36°F to 54°F. Average High and Low Temperature in January in Guidonia Montecelio
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 Guidonia Montecelio
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.
Meadow Vista, California, United States (6,139 miles away) is the far-away foreign place with temperatures most similar to Guidonia Montecelio (view comparison). CloudsThe month of January in Guidonia Montecelio experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 48% throughout the month. The clearest day of the month is January 30, with clear, mostly clear, or partly cloudy conditions 53% of the time. For reference, on November 29, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 51%, while on July 21, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 87%. Cloud Cover Categories in January in Guidonia Montecelio
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.
Compare Guidonia Montecelio to:PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Guidonia Montecelio, the chance of a wet day over the course of January is gradually increasing, starting the month at 21% and ending it at 24%. For reference, the year's highest daily chance of a wet day is 33% on November 19, and its lowest chance is 9% on August 9. Probability of Precipitation in January in Guidonia Montecelio
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).
RainfallTo 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 Guidonia Montecelio is essentially constant, remaining about 2.1 inches throughout, and rarely exceeding 4.3 inches or falling below 0.3 inches. The lowest average 31-day accumulation is 2.0 inches on January 10. Average Monthly Rainfall in January in Guidonia Montecelio
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.
SunOver the course of January in Guidonia Montecelio, the length of the day is increasing. From the start to the end of the month, the length of the day increases by 48 minutes, implying an average daily increase of 1 minute, 37 seconds, and weekly increase of 11 minutes, 17 seconds. The shortest day of the month is January 1, with 9 hours, 11 minutes of daylight and the longest day is January 31, with 10 hours, 0 minutes of daylight. Hours of Daylight and Twilight in January in Guidonia Montecelio
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 Guidonia Montecelio is 7:37 AM on January 3 and the earliest sunrise is 14 minutes earlier at 7:23 AM on January 31. The earliest sunset is 4:48 PM on January 1 and the latest sunset is 34 minutes later at 5:22 PM on January 31. Daylight saving time is observed in Guidonia Montecelio during 2026, but it neither starts nor ends during January, so the entire month is in standard time. For reference, on June 21, the longest day of the year, the Sun rises at 5:33 AM and sets 15 hours, 15 minutes later, at 8:48 PM, while on December 21, the shortest day of the year, it rises at 7:33 AM and sets 9 hours, 7 minutes later, at 4:40 PM. Sunrise & Sunset with Twilight in January in Guidonia Montecelio
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 Guidonia Montecelio
northeastsouthwest
Solar elevation and azimuth over the course of January 2026. 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).
MoonThe figure below presents a compact representation of key lunar data for January 2026. 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 Guidonia Montecelio
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.
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 Guidonia Montecelio is essentially constant during January, remaining around 0% throughout. For reference, on August 13, the muggiest day of the year, there are muggy conditions 42% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% 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 Guidonia Montecelio is essentially constant during January, remaining within 0.1 miles per hour of 6.8 miles per hour throughout. For reference, on April 3, the windiest day of the year, the daily average wind speed is 7.6 miles per hour, while on August 28, the calmest day of the year, the daily average wind speed is 6.3 miles per hour. The lowest daily average wind speed during January is 6.7 miles per hour on January 21. The hourly average wind direction in Guidonia Montecelio throughout January is predominantly from the east, with a peak proportion of 38% on January 5. Wind Direction in January in Guidonia Montecelio
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).
Water TemperatureGuidonia Montecelio 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 Guidonia Montecelio is gradually decreasing during January, falling by 2°F, from 59°F to 58°F, over the course of the month. 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). The growing season in Guidonia Montecelio typically lasts for 9.1 months (280 days), from around March 1 to around December 6, rarely starting before February 6 or after March 30, and rarely ending before November 9 or after December 29. The month of January in Guidonia Montecelio is very likely fully outside of the growing season, with the chance that a given day is in the growing season reaching a low of 1% on January 16. Time Spent in Various Temperature Bands and the Growing Season in January in Guidonia Montecelio
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 Guidonia Montecelio are essentially constant during January, remaining within 17°F of 18°F throughout. 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 Guidonia Montecelio is gradually increasing during January, rising by 0.6 kWh, from 1.8 kWh to 2.4 kWh, over the course of the month. TopographyFor the purposes of this report, the geographical coordinates of Guidonia Montecelio are 41.994 deg latitude, 12.722 deg longitude, and 302 ft elevation. The topography within 2 miles of Guidonia Montecelio contains significant variations in elevation, with a maximum elevation change of 725 feet and an average elevation above sea level of 346 feet. Within 10 miles contains significant variations in elevation (4,075 feet). Within 50 miles also contains extreme variations in elevation (8,110 feet). The area within 2 miles of Guidonia Montecelio is covered by cropland (74%) and artificial surfaces (16%), within 10 miles by cropland (65%) and trees (20%), and within 50 miles by cropland (40%) and trees (30%). Data SourcesThis report illustrates the typical weather in Guidonia Montecelio, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. Temperature and Dew PointThere are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Guidonia Montecelio. For each station, the records are corrected for the elevation difference between that station and Guidonia Montecelio 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 Guidonia Montecelio is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Guidonia Montecelio 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 Guidonia Montecelio 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 DataAll 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. 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. Please review our full terms contained on our Terms of Service page. |
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