Average Weather in Arcata California, United States
In Arcata, the summers are comfortable, dry, and mostly clear and the winters are long, cold, wet, and mostly cloudy. Over the course of the year, the temperature typically varies from 41°F to 67°F and is rarely below 32°F or above 74°F.
The warm season lasts for 3.5 months, from June 28 to October 12, with an average daily high temperature above 64°F. The hottest day of the year is September 11, with an average high of 67°F and low of 51°F.
The cool season lasts for 4.2 months, from November 26 to April 2, with an average daily high temperature below 57°F. The coldest day of the year is December 23, with an average low of 41°F and high of 55°F.
Average High and Low Temperature
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, 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 Arcata, the average percentage of the sky covered by clouds experiences extreme seasonal variation over the course of the year.
The clearer part of the year in Arcata begins around June 1 and lasts for 4.5 months, ending around October 16. On August 3, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 89% of the time, and overcast or mostly cloudy 11% of the time.
The cloudier part of the year begins around October 16 and lasts for 7.5 months, ending around June 1. On January 9, the cloudiest day of the year, the sky is overcast or mostly cloudy 68% of the time, and clear, mostly clear, or partly cloudy 32% of the time.
Cloud Cover Categories
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Arcata varies significantly throughout the year.
The wetter season lasts 6.1 months, from October 24 to April 26, with a greater than 24% chance of a given day being a wet day. The chance of a wet day peaks at 47% on December 4.
The drier season lasts 5.9 months, from April 26 to October 24. The smallest chance of a wet day is 1% on August 3.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 46% on December 1.
Daily Chance of Precipitation
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Arcata experiences extreme seasonal variation in monthly rainfall.
The rainy period of the year lasts for 9.3 months, from September 9 to June 19, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around December 13, with an average total accumulation of 9.0 inches.
The rainless period of the year lasts for 2.7 months, from June 19 to September 9. The least rain falls around July 30, with an average total accumulation of 0.1 inches.
Average Monthly Rainfall
The length of the day in Arcata varies significantly over the course of the year. In 2017, the shortest day is December 21, with 9 hours, 14 minutes of daylight; the longest day is June 20, with 15 hours, 7 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:44 AM on June 13, and the latest sunrise is 2 hours, 7 minutes later at 7:50 AM on November 4. The earliest sunset is at 4:48 PM on December 6, and the latest sunset is 4 hours, 4 minutes later at 8:52 PM on June 27.
Daylight saving time (DST) is observed in Arcata during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.
Sunrise & Sunset with Twilight and Daylight Saving Time
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 perceived humidity level in Arcata, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.
Humidity Comfort Levels
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 Arcata experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 5.0 months, from November 17 to April 18, with average wind speeds of more than 4.2 miles per hour. The windiest day of the year is December 13, with an average hourly wind speed of 4.8 miles per hour.
The calmer time of year lasts for 7.0 months, from April 18 to November 17. The calmest day of the year is September 25, with an average hourly wind speed of 3.7 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Arcata varies throughout the year.
The wind is most often from the north for 8.0 months, from March 13 to November 13, with a peak percentage of 78% on July 18. The wind is most often from the south for 4.0 months, from November 13 to March 13, with a peak percentage of 41% on January 1.
Arcata 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 water temperature does not vary significantly over the course of the year, remaining within 2°F of 53°F throughout.
Average Water Temperature
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 experiences extreme seasonal variation over the course of the year.
The brighter period of the year lasts for 3.3 months, from May 17 to August 26, with an average daily incident shortwave energy per square meter above 6.8 kWh. The brightest day of the year is June 30, with an average of 8.1 kWh.
The darker period of the year lasts for 3.8 months, from October 31 to February 23, with an average daily incident shortwave energy per square meter below 2.9 kWh. The darkest day of the year is December 26, with an average of 1.5 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Arcata are 40.867 deg latitude, -124.083 deg longitude, and 26 ft elevation.
The topography within 2 miles of Arcata contains very significant variations in elevation, with a maximum elevation change of 1,050 feet and an average elevation above sea level of 132 feet. Within 10 miles contains very significant variations in elevation (2,635 feet). Within 50 miles contains large variations in elevation (7,454 feet).
The area within 2 miles of Arcata is covered by herbaceous vegetation (53%), trees (25%), and cropland (12%), within 10 miles by trees (46%) and water (28%), and within 50 miles by trees (42%) and water (42%).
This report illustrates the typical weather in Arcata, 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 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Arcata.
For each station, the records are corrected for the elevation difference between that station and Arcata 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 Arcata is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Arcata and a given station.
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , 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 aiports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.