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December Weather in Rialto, United States

Last updated: June 24, 2025

In December, the average temperature in Rialto, United States hovers around 11°C (51°F), making it a cool yet pleasant time of the year. Expect a minimum chill of -1°C (30°F) and a warm peak of 27°C (80°F). During this month, you can anticipate 70 mm (2.7 in) of precipitation, spread over about 5 days, with a 74% average humidity adding to the overall atmosphere. 🌦️

December Temperature in Rialto

In December in Rialto, the average temperature is 11°C (51°F). Maximums can reach 27°C (80°F) and minimums can be as low as -1°C (30°F). Be prepared for a range of temperatures and pack accordingly for your trip!

December Weather in Rialto: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Rialto, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Rialto, December typically has an average temperature of 11°C (51°F), with highs reaching up to 27°C (80°F) and lows dropping to around -1°C (30°F).
JanFebMarAprMayJunJulAugSepOctNovDec515154606472787874665951
Data source: Temperature data for Rialto generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

December Precipitation in Rialto

In Rialto in December, the total precipitation amount is 70 mm (2.7 in) over the course of 5 days.

December Precipitation Trends in Rialto

The chart displays monthly precipitation patterns in Rialto, with values for each month alongside December’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December’s conditions compare to those of other months. In Rialto, December typically receives around 70 mm (2.7 inches) of precipitation spread over approximately 5 days.
JanFebMarAprMayJunJulAugSepOctNovDec70707531183111010112870
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Rialto

In Rialto in December, humidity is 74%. With an average temperature of 11°C (51°F), this humidity feels like a damp chill that seeps into your bones, making outdoor exploration a bit uncomfortable and encouraging visitors to seek refuge in cozy cafés or indoor attractions.

December Average Humidity in Rialto

This chart illustrates the average monthly humidity levels in Rialto, with December’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In December, average humidity in Rialto is approximately 74%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec72%77%67%56%46%48%46%42%52%58%66%74%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Rialto

In Rialto in December, the maximum UV index reaches 4, which corresponds to a moderate Exposure Category. With a time to burn of 30 minutes, it’s important to take precautions to protect your skin. You can find more details in the Hourly UV Index in Rialto for better planning.

Maximum UV Index Levels in Rialto for December

The chart shows the monthly maximum UV Index (UVI) for Rialto in December, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In December, the maximum UV index in Rialto typically reaches 4, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec469101112121110854
Data source: Rialto December UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How December Weather in Rialto Compares to Other Months

Weather in Rialto varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Rialto, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Rialto, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather11°C (51°F)70 mm (2.8 inches)72%moderate
February Weather11°C (52°F)70 mm (2.7 inches)77%high
March Weather12°C (54°F)75 mm (2.9 inches)67%very high
April Weather16°C (61°F)31 mm (1.2 inches)56%very high
May Weather18°C (64°F)18 mm (0.7 inches)46%extreme
June Weather22°C (72°F)3 mm (0.1 inches)48%extreme
July Weather26°C (78°F)11 mm (0.4 inches)46%extreme
August Weather26°C (79°F)10 mm (0.4 inches)42%extreme
September Weather23°C (74°F)10 mm (0.4 inches)52%very high
October Weather19°C (66°F)11 mm (0.4 inches)58%very high
November Weather15°C (59°F)28 mm (1.1 inches)66%moderate
December Weather11°C (51°F)70 mm (2.7 inches)74%moderate

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