January Weather in Tempe Arizona, United StatesDaily high temperatures increase by 3°F, from 65°F to 68°F, rarely falling below 57°F or exceeding 77°F. Daily low temperatures increase by 2°F, from 44°F to 46°F, rarely falling below 36°F or exceeding 54°F. For reference, on July 2, the hottest day of the year, temperatures in Tempe typically range from 83°F to 106°F, while on December 27, the coldest day of the year, they range from 44°F to 65°F. 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. Ouargla, Algeria (6,355 miles away) is the far-away foreign place with temperatures most similar to Tempe (view comparison). CloudsThe month of January in Tempe experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 34% throughout the month. The clearest day of the month is January 22, with clear, mostly clear, or partly cloudy conditions 67% of the time. For reference, on February 19, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 38%, while on June 13, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 85%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Tempe, the chance of a wet day over the course of January is essentially constant, remaining around 11% throughout. For reference, the year's highest daily chance of a wet day is 21% on August 3, and its lowest chance is 1% on June 12. 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 Tempe is essentially constant, remaining about 1.1 inches throughout, and rarely exceeding 3.0 inches. SunOver the course of January in Tempe, the length of the day is increasing. From the start to the end of the month, the length of the day increases by 34 minutes, implying an average daily increase of 1 minute, 9 seconds, and weekly increase of 8 minutes, 0 seconds. The shortest day of the month is January 1, with 9 hours, 59 minutes of daylight and the longest day is January 31, with 10 hours, 33 minutes of daylight. The latest sunrise of the month in Tempe is 7:32 AM on January 8 and the earliest sunrise is 8 minutes earlier at 7:24 AM on January 31. The earliest sunset is 5:30 PM on January 1 and the latest sunset is 27 minutes later at 5:57 PM on January 31. Daylight saving time is not observed in Tempe during 2024. For reference, on June 20, the longest day of the year, the Sun rises at 5:18 AM and sets 14 hours, 22 minutes later, at 7:40 PM, while on December 21, the shortest day of the year, it rises at 7:27 AM and sets 9 hours, 56 minutes later, at 5:24 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 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.
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 Tempe is essentially constant during January, remaining around 0% throughout. For reference, on August 4, the muggiest day of the year, there are muggy conditions 24% of the time, while on November 3, 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 Tempe is essentially constant during January, remaining within 0.1 miles per hour of 6.8 miles per hour throughout. For reference, on April 29, the windiest day of the year, the daily average wind speed is 7.5 miles per hour, while on August 15, the calmest day of the year, the daily average wind speed is 5.7 miles per hour. The highest daily average wind speed during January is 6.9 miles per hour on January 6. The hourly average wind direction in Tempe throughout January is predominantly from the east, with a peak proportion of 54% on January 8. 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 Tempe 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 Tempe are increasing during January, increasing by 200°F, from 6°F to 206°F, over the course of the month. 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 Tempe is gradually increasing during January, rising by 0.7 kWh, from 3.2 kWh to 3.9 kWh, over the course of the month. TopographyFor the purposes of this report, the geographical coordinates of Tempe are 33.415 deg latitude, -111.909 deg longitude, and 1,181 ft elevation. The topography within 2 miles of Tempe contains only modest variations in elevation, with a maximum elevation change of 269 feet and an average elevation above sea level of 1,179 feet. Within 10 miles contains only modest variations in elevation (1,588 feet). Within 50 miles contains very significant variations in elevation (6,877 feet). The area within 2 miles of Tempe is covered by artificial surfaces (71%) and shrubs (29%), within 10 miles by artificial surfaces (57%) and shrubs (36%), and within 50 miles by shrubs (84%). Data SourcesThis report illustrates the typical weather in Tempe, 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 Tempe. For each station, the records are corrected for the elevation difference between that station and Tempe 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 Tempe is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Tempe 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 Tempe 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. |