Climate and Average Weather Year Round at Gillespie Field United States

At Gillespie Field, the summers are short, hot, arid, and mostly clear and the winters are long, cool, and partly cloudy. Over the course of the year, the temperature typically varies from 40°F to 88°F and is rarely below 34°F or above 97°F.

Based on the tourism score, the best time of year to visit Gillespie Field for warm-weather activities is from late May to early October.

The hot season lasts for 2.7 months, from July 3 to September 25, with an average daily high temperature above 84°F. The hottest month of the year at Gillespie Field is August, with an average high of 88°F and low of 64°F.

The cool season lasts for 4.3 months, from November 27 to April 5, with an average daily high temperature below 72°F. The coldest month of the year at Gillespie Field is December, with an average low of 41°F and high of 69°F.

At Gillespie Field, 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 Gillespie Field begins around May 2 and lasts for 6.0 months, ending around November 2.

The clearest month of the year at Gillespie Field is September, 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 6.0 months, ending around May 2.

The cloudiest month of the year at Gillespie Field is February, during which on average the sky is overcast or mostly cloudy 43% 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 Gillespie Field varies throughout the year.

The wetter season lasts 4.7 months, from November 17 to April 9, with a greater than 11% chance of a given day being a wet day. The month with the most wet days at Gillespie Field is February, with an average of 5.7 days with at least 0.04 inches of precipitation.

The drier season lasts 7.3 months, from April 9 to November 17. The month with the fewest wet days at Gillespie Field is June, with an average of 0.2 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 Gillespie Field is February, with an average of 5.7 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 21% on February 21.

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. Gillespie Field experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 6.2 months, from October 17 to April 24, with a sliding 31-day rainfall of at least 0.5 inches. The month with the most rain at Gillespie Field is February, with an average rainfall of 2.5 inches.

The rainless period of the year lasts for 5.8 months, from April 24 to October 17. The month with the least rain at Gillespie Field is June, with an average rainfall of 0.0 inches.

The length of the day at Gillespie Field varies significantly over the course of the year. In 2024, the shortest day is December 21, with 9 hours, 59 minutes of daylight; the longest day is June 20, with 14 hours, 19 minutes of daylight.

The earliest sunrise is at 5:39 AM on June 11, and the latest sunrise is 1 hour, 28 minutes later at 7:07 AM on November 2. The earliest sunset is at 4:41 PM on December 3, and the latest sunset is 3 hours, 19 minutes later at 8:00 PM on June 28.

Daylight saving time (DST) is observed at Gillespie Field during 2024, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.

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

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 Gillespie Field, 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 4% of 4% 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 Gillespie Field experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 7.1 months, from November 11 to June 15, with average wind speeds of more than 7.0 miles per hour. The windiest month of the year at Gillespie Field is December, with an average hourly wind speed of 8.0 miles per hour.

The calmer time of year lasts for 4.9 months, from June 15 to November 11. The calmest month of the year at Gillespie Field is September, with an average hourly wind speed of 6.0 miles per hour.

The predominant average hourly wind direction at Gillespie Field varies throughout the year.

The wind is most often from the west for 9.6 months, from February 1 to November 19, with a peak percentage of 81% on June 2. The wind is most often from the east for 2.4 months, from November 19 to February 1, with a peak percentage of 45% on January 1.

Gillespie Field 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 2.9 months, from July 10 to October 5, with an average temperature above 68°F. The month of the year at Gillespie Field with the warmest water is August, with an average temperature of 70°F.

The time of year with cooler water lasts for 4.4 months, from December 8 to April 19, with an average temperature below 61°F. The month of the year at Gillespie Field with the coolest water is February, with an average temperature of 59°F.

To characterize how pleasant the weather is at Gillespie Field 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 Gillespie Field for general outdoor tourist activities is from late May to early October, with a peak score in the last week of June.

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 Gillespie Field for hot-weather activities is from mid July to early September, with a peak score in the third week of August.

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).

While it does not do so every year, freezing temperatures are seen at Gillespie Field over some winters. The day least likely to be in the growing season is December 30, with a 61% chance.

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.

Based on growing degree days alone, the first spring blooms at Gillespie Field should appear around January 16, only rarely appearing before January 12 or after January 22.

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 3.7 months, from April 24 to August 16, with an average daily incident shortwave energy per square meter above 7.4 kWh. The brightest month of the year at Gillespie Field is June, with an average of 8.4 kWh.

The darker period of the year lasts for 3.2 months, from November 5 to February 12, with an average daily incident shortwave energy per square meter below 4.2 kWh. The darkest month of the year at Gillespie Field is December, with an average of 3.2 kWh.

For the purposes of this report, the geographical coordinates of Gillespie Field are 32.826 deg latitude, -116.973 deg longitude, and 367 ft elevation.

The topography within 2 miles of Gillespie Field contains very significant variations in elevation, with a maximum elevation change of 850 feet and an average elevation above sea level of 464 feet. Within 10 miles contains very significant variations in elevation (3,107 feet). Within 50 miles contains large variations in elevation (6,483 feet).

The area within 2 miles of Gillespie Field is covered by artificial surfaces (85%) and shrubs (15%), within 10 miles by shrubs (44%) and artificial surfaces (41%), and within 50 miles by shrubs (45%) and water (32%).