Climate and Average Weather Year Round at San Nicholas Island California, United States

At San Nicholas Island, the summers are arid, mostly clear, and comfortable; the winters are long, cool, and partly cloudy; and it is windy year round. Over the course of the year, the temperature typically varies from 52°F to 75°F and is rarely below 47°F or above 84°F.

Based on the tourism score, the best time of year to visit San Nicholas Island for warm-weather activities is from late June to mid October.

The warm season lasts for 3.2 months, from July 9 to October 17, with an average daily high temperature above 73°F. The hottest month of the year at San Nicholas Island is September, with an average high of 75°F and low of 61°F.

The cool season lasts for 4.4 months, from November 30 to April 13, with an average daily high temperature below 67°F. The coldest month of the year at San Nicholas Island is February, with an average low of 53°F and high of 65°F.

At San Nicholas Island, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.

The clearer part of the year at San Nicholas Island begins around April 26 and lasts for 6.2 months, ending around November 2.

The clearest month of the year at San Nicholas Island is August, during which on average the sky is clear, mostly clear, or partly cloudy 89% of the time.

The cloudier part of the year begins around November 2 and lasts for 5.8 months, ending around April 26.

The cloudiest month of the year at San Nicholas Island is February, during which on average the sky is overcast or mostly cloudy 41% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days at San Nicholas Island varies throughout the year.

The wetter season lasts 4.3 months, from November 22 to March 31, with a greater than 10% chance of a given day being a wet day. The month with the most wet days at San Nicholas Island is February, with an average of 5.0 days with at least 0.04 inches of precipitation.

The drier season lasts 7.8 months, from March 31 to November 22. The month with the fewest wet days at San Nicholas Island is August, with an average of 0.0 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone at San Nicholas Island is February, with an average of 5.0 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 20% on February 20.

Rainfall

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. San Nicholas Island experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 5.6 months, from October 30 to April 19, with a sliding 31-day rainfall of at least 0.5 inches. The month with the most rain at San Nicholas Island is February, with an average rainfall of 2.4 inches.

The rainless period of the year lasts for 6.4 months, from April 19 to October 30. The month with the least rain at San Nicholas Island is August, with an average rainfall of 0.0 inches.

The length of the day at San Nicholas Island varies significantly over the course of the year. In 2026, the shortest day is December 21, with 9 hours, 57 minutes of daylight; the longest day is June 21, with 14 hours, 21 minutes of daylight.

The earliest sunrise is at 5:48 AM on June 11, and the latest sunrise is 1 hour, 29 minutes later at 7:17 AM on March 8. The earliest sunset is at 4:50 PM on December 4, and the latest sunset is 3 hours, 21 minutes later at 8:11 PM on June 29.

Daylight saving time (DST) is observed at San Nicholas Island during 2026, starting in the spring on March 8, lasting 7.8 months, and ending in the fall on November 1.

The figure below presents a compact representation of key lunar data for 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.

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 at San Nicholas Island, 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, staying within 1% of 1% throughout.

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 at San Nicholas Island experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 3.5 months, from March 1 to June 16, with average wind speeds of more than 12.9 miles per hour. The windiest month of the year at San Nicholas Island is April, with an average hourly wind speed of 14.6 miles per hour.

The calmer time of year lasts for 8.5 months, from June 16 to March 1. The calmest month of the year at San Nicholas Island is October, with an average hourly wind speed of 11.3 miles per hour.

The predominant average hourly wind direction at San Nicholas Island varies throughout the year.

The wind is most often from the west for 11 months, from January 6 to December 10, with a peak percentage of 87% on August 13. The wind is most often from the north for 3.9 weeks, from December 10 to January 6, with a peak percentage of 39% on January 1.

San Nicholas Island 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 experiences some seasonal variation over the course of the year.

The time of year with warmer water lasts for 3.2 months, from July 16 to October 21, with an average temperature above 64°F. The month of the year at San Nicholas Island with the warmest water is August, with an average temperature of 65°F.

The time of year with cooler water lasts for 5.3 months, from December 13 to May 22, with an average temperature below 59°F. The month of the year at San Nicholas Island with the coolest water is March, with an average temperature of 58°F.

To characterize how pleasant the weather is at San Nicholas Island throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit San Nicholas Island for general outdoor tourist activities is from late June to mid October, with a peak score in the second week of September.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit San Nicholas Island for hot-weather activities is from mid August to late September, with a peak score in the second week of September.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions 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 at San Nicholas Island 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.

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 4.0 months, from April 24 to August 24, with an average daily incident shortwave energy per square meter above 7.2 kWh. The brightest month of the year at San Nicholas Island is June, with an average of 8.2 kWh.

The darker period of the year lasts for 3.1 months, from November 6 to February 11, with an average daily incident shortwave energy per square meter below 4.1 kWh. The darkest month of the year at San Nicholas Island is December, with an average of 3.1 kWh.

For the purposes of this report, the geographical coordinates of San Nicholas Island are 33.235 deg latitude, -119.453 deg longitude, and 505 ft elevation.

The topography within 2 miles of San Nicholas Island contains significant variations in elevation, with a maximum elevation change of 801 feet and an average elevation above sea level of 197 feet. Within 10 miles contains significant variations in elevation (906 feet). Within 50 miles also contains very significant variations in elevation (906 feet).

The area within 2 miles of San Nicholas Island is covered by water (49%), shrubs (25%), and grassland (16%), within 10 miles by water (93%), and within 50 miles by water (100%).