Average Weather in January in Pomona California, United States
Daily high temperatures are around 67°F, rarely falling below 56°F or exceeding 79°F.
Daily low temperatures are around 44°F, rarely falling below 36°F or exceeding 52°F.
For reference, on August 22, the hottest day of the year, temperatures in Pomona typically range from 65°F to 92°F, while on December 25, the coldest day of the year, they range from 43°F to 66°F.
Average High and Low Temperature in January
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
The month of January in Pomona experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 39% throughout the month.
The clearest day of the month is January 21, with clear, mostly clear, or partly cloudy conditions 62% of the time.
For reference, on February 20, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 44%, while on September 7, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 91%.
Cloud Cover Categories in January
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. In Pomona, the chance of a wet day over the course of January is essentially constant, remaining around 16% throughout.
For reference, the year's highest daily chance of a wet day is 20% on February 20, and its lowest chance is 0% on June 23.
Probability of Precipitation in January
The average sliding 31-day rainfall during January in Pomona is essentially constant, remaining about 2.5 inches throughout, and rarely exceeding 7.3 inches or falling below 0.1 inches.
Average Monthly Rainfall in January
Over the course of January in Pomona, the length of the day is increasing. From the start to the end of the month, the length of the day increases by 36 minutes, implying an average daily increase of 1 minute, 12 seconds, and weekly increase of 8 minutes, 21 seconds.
The shortest day of the month is January 1, with 9 hours, 56 minutes of daylight and the longest day is January 31, with 10 hours, 32 minutes of daylight.
Hours of Daylight and Twilight in January
The latest sunrise of the month in Pomona is 6:57 AM on January 7 and the earliest sunrise is 9 minutes earlier at 6:48 AM on January 31.
The earliest sunset is 4:52 PM on January 1 and the latest sunset is 28 minutes later at 5:20 PM on January 31.
Daylight saving time is observed in Pomona during 2018, 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 5:40 AM and sets 14 hours, 26 minutes later, at 8:05 PM, while on December 21, the shortest day of the year, it rises at 6:52 AM and sets 9 hours, 53 minutes later, at 4:45 PM.
Sunrise & Sunset with Twilight in January
The chance that a given day will be muggy in Pomona is essentially constant during January, remaining around 0% throughout.
For reference, on August 11, the muggiest day of the year, there are muggy conditions 6% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in January
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Pomona is essentially constant during January, remaining within 0.2 miles per hour of 7.5 miles per hour throughout.
For reference, on December 31, the windiest day of the year, the daily average wind speed is 7.8 miles per hour, while on September 8, the calmest day of the year, the daily average wind speed is 5.2 miles per hour.
Average Wind Speed in January
Wind Direction in January
Pomona 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 Pomona is essentially constant during January, remaining around 59°F throughout.
Average Water Temperature in January
Temperatures in Pomona 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.
Time Spent in Various Temperature Bands and the Growing Season in January
The average accumulated growing degree days in Pomona are increasing during January, increasing by 186°F, from 0°F to 186°F, over the course of the month.
Growing Degree Days in January
The average daily incident shortwave solar energy in Pomona is gradually increasing during January, rising by 0.7 kWh, from 3.0 kWh to 3.7 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in January
For the purposes of this report, the geographical coordinates of Pomona are 34.055 deg latitude, -117.752 deg longitude, and 886 ft elevation.
The topography within 2 miles of Pomona contains only modest variations in elevation, with a maximum elevation change of 456 feet and an average elevation above sea level of 859 feet. Within 10 miles contains only modest variations in elevation (5,000 feet). Within 50 miles also contains extreme variations in elevation (10,807 feet).
The area within 2 miles of Pomona is covered by artificial surfaces (81%) and shrubs (19%), within 10 miles by artificial surfaces (55%) and shrubs (33%), and within 50 miles by shrubs (51%) and artificial surfaces (23%).
This report illustrates the typical weather in Pomona year round, 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 Pomona.
For each station, the records are corrected for the elevation difference between that station and Pomona 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 Pomona is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Pomona and a given station.
The stations contributing to this reconstruction are: Ontario International Airport (60%, 10 kilometers, east); Chino Airport (31%, 14 kilometers, southeast); Fullerton Municipal Airport (8%, 29 kilometers, southwest); and Mount Wilson (1.0%, 35 kilometers, northwest).
Time zones for aiports and weather stations are provided by AskGeo.com .