San Diego Weather for December begins with crisp mornings and gradually warms up throughout the day, as San Diego starts to transition from autumn’s cool breeze to winter’s mild temperatures. The average high temperature in December is a pleasant 18°C (64°F), while the average low is a cool 9°C (48°F). This gradual warming is one of the factors that makes San Diego a favorite among tourists during the winter months.
The city experiences an average of 3 to 4 rainy days in December, with an average rainfall of around 62 mm (2.4 in). Although this is relatively dry compared to other months, the rain is often accompanied by strong winds and storms that can cause flash flooding. In addition, the overcast skies and grey rainclouds often lead to cooler temperatures and rough sea conditions perfect for surfing.
Temperature Trends in San Diego for December
San Diego, known for its mild Mediterranean climate, experiences a gradual cooling in December, marking the beginning of the winter season. While temperatures can fluctuate, the city’s average high temperature typically ranges from the mid-60s to mid-70s (°F), while the average low temperature can dip to the mid-40s to mid-50s. This variation creates opportunities for pleasant winter days with comfortable temperatures, perfect for outdoor activities, such as hiking or visits to local beaches.
Average High and Low Temperatures in San Diego for December
According to the National Centers for Environmental Information (NCEI), San Diego’s average high temperature in December is around 67°F (19.4°C), while the average low temperature is approximately 48°F (8.9°C). The warmest day of the month often occurs around December 1st, with temperatures sometimes reaching the mid-70s (°F). Conversely, the coldest day usually falls around December 20th, with temperatures sometimes dropping to the mid-40s (°F).
Coldest and Warmest Days in December
The following temperatures are examples of the lowest and highest recorded temperatures in San Diego for December over the years:
- Coldest recorded temperature: 29°F (-2.2°C) on December 17, 2000
- Warmest recorded temperature: 79°F (26.1°C) on December 5, 1988
- Lowest temperature in last 10 years: 36°F (2.2°C) on December 20, 2013
- Warmest temperature in last 10 years: 72°F (22.2°C) on December 1, 2016
Factors Influencing Temperature Trends in San Diego
Temperature trends in San Diego are influenced by various factors, including:
- El Niño and La Niña Events
- North Pacific High (Pineapple Express)
- California Current
- Land and Sea Breezes
- Temperature inversions
- Mountainous terrain
- Urban Heat Island effect
El Niño and La Niña Effects on San Diego’s Temperature
These two significant climate phenomena can significantly influence San Diego’s temperature trends due to their impact on atmospheric circulation. Both El Niño and La Niña events can cause changes in temperature patterns across the Pacific Ocean.
- El Niño: Warmer ocean temperatures lead to higher atmospheric temperatures in San Diego, resulting in warmer winters.
- La Niña: Colder ocean temperatures lead to cooler atmospheric temperatures in San Diego, resulting in colder winters.
North Pacific High (Pineapple Express) and Temperature Trends
This phenomenon occurs when a high-pressure system develops over the North Pacific Ocean, pulling warm, moist air towards the Pacific Northwest. The warm moist air can affect San Diego’s temperature, making it milder.
- Pineapple Express events can lead to higher temperatures in San Diego.
California Current and its Impact on Temperature Trends
The California Current is a cold-water current that runs along the west coast of North America. Its influence can be significant in San Diego, as it can help maintain cooler temperatures in the area.
- The California Current helps regulate San Diego’s temperature.
Land and Sea Breezes and Temperature Trends
Land and sea breezes play a significant role in San Diego’s temperature, as they contribute to cooling or warming temperatures based on diurnal cycles.
- Sea breezes can cool San Diego temperatures during the day.
- Land breezes can warm San Diego temperatures at night.
Temperature Inversions and Temperature Trends
Temperature inversions can also impact San Diego’s temperature trends. When a layer of warm air blankets a layer of cool air, it can result in higher temperatures at higher elevations.
- Temperature inversions can cause cooler temperatures in urban areas.
Mountainous Terrain and Temperature Trends
San Diego’s mountainous terrain plays a crucial role in temperature trends. Mountainous areas tend to be cooler than the surrounding lower-lying areas due to the presence of cooler air masses.
- Mountainous terrain can cause temperature variations.
Urban Heat Island Effect and Temperature Trends, San diego weather for december
Urban Heat Island (UHI) effect occurs when built-up areas absorb and retain heat, leading to warmer temperatures compared to surrounding rural areas.
- Urban areas of San Diego can experience warmer temperatures due to the UHI effect.
Rainfall Patterns in San Diego for December
December in San Diego brings a mix of rainfall and relatively mild temperatures, offering a respite from the hotter summer months. The region’s coastal influence keeps temperatures moderate, with average highs in the mid-60s Fahrenheit (18°C).
San Diego’s rainfall patterns during December are characterized by a relatively low number of rainy days, with an average of around 6-7 days of measurable precipitation throughout the month. The average amount of rainfall for December is around 2-3 inches (50-75 mm), with most of it coming from short-duration storms. These storms can be intense, with heavy rainfall and gusty winds, but they are relatively rare.
Sudden Storms and Flash Flooding
Flash flooding can be a concern in San Diego, particularly in urban areas where storm drains are overwhelmed. The risk is higher during intense rainfall events, which are often associated with cold fronts that bring warm, moist air from the Pacific Ocean. This can lead to heavy rainfall in a short period, causing rapid runoff and increased risk of flash flooding.
Top 5 Rainiest Decembers in San Diego’s History
- 1983: A strong low-pressure system brought heavy rainfall to the region, resulting in a total of 6.55 inches (166 mm) of rain on December 18. This event also saw strong winds, with gusts reaching up to 90 mph (145 km/h).
- 1953: A prolonged period of rainfall, lasting several days, brought a total of 5.65 inches (144 mm) to the region. Temperatures were also relatively warm, with highs reaching the mid-60s (18°C).
- 1978: A cold front swept through the region, dropping temperatures and bringing heavy rainfall. The total rainfall for the month was 5.45 inches (139 mm), with some areas receiving over 6 inches (152 mm).
- 1981: A tropical cyclone, classified as a subtropical storm, brought heavy rainfall to the region. The total rainfall for the month was 5.25 inches (133 mm), with some areas receiving over 7 inches (178 mm).
- 2010: A low-pressure system lingered over the region, bringing heavy rainfall and strong winds. The total rainfall for the month was 5.15 inches (131 mm), with some areas receiving over 6 inches (152 mm).
Sunshine Hours in San Diego for December
San Diego, known for its mild Mediterranean climate, offers ample opportunities to soak up the sun throughout the year. While December is one of the cooler months, the city still averages a significant amount of sunshine, making it an ideal spot for outdoor enthusiasts.
Sunshine hours in San Diego during December typically range from 7 to 8 hours per day, with an average of 7.5 hours of direct sunlight. This amount of sunlight, combined with the mild temperatures, contributes to San Diego’s reputation as a sun-kissed destination.
The Relationship Between Sunshine Hours and Temperature
Sunshine hours play a crucial role in regulating San Diego’s temperature. When the sun is out, it warms the atmosphere, resulting in warmer temperatures during the day. However, as the sun sets, the temperatures drop, causing the cooler night air to settle. This diurnal temperature variation is a common phenomenon in Mediterranean climates like San Diego’s.
Sunshine hours can also impact temperature through the process of evaporative cooling. When the sun heats the surface of the ocean, it evaporates water into the air, which in turn cools the surrounding environment. This process is particularly effective during the early morning hours, when the sun’s rays are still low in the sky.
The relationship between sunshine hours and temperature is complex and influenced by various factors, including cloud cover, atmospheric circulation patterns, and the amount of atmospheric moisture. Understanding this relationship helps scientists and enthusiasts alike make more accurate predictions about San Diego’s weather patterns.
The Effects of Overcast Skies
Overcast skies can have a significant impact on San Diego’s weather patterns. When the sky is covered in clouds, the city experiences a reduction in the amount of direct sunlight it receives. This can lead to cooler temperatures, as the clouds block the warming effects of the sun.
In addition to temperature, overcast skies can also affect precipitation patterns. When the atmosphere is saturated with moisture and there is a lack of direct sunlight, precipitation becomes more likely. This is because the clouds trap heat and moisture, creating an environment conducive to precipitation.
Ocean currents are also affected by overcast skies. When the sun is not shining, the ocean surface temperature cools, which in turn affects the ocean’s thermal dynamics. This can impact the distribution of marine life, as species that are sensitive to temperature and water quality may struggle to survive in areas with reduced sunlight.
In summary, sunshine hours in San Diego during December play a crucial role in regulating the city’s temperature, precipitation patterns, and ocean currents. Understanding the complex relationships between these factors can help scientists, residents, and visitors alike better appreciate the beauty and complexities of San Diego’s climate.
Fog and Mist in San Diego for December
Fog and mist are common weather phenomena in San Diego during December, characterized by low-lying clouds and visibility reduction. San Diego’s marine climate, with its proximity to the Pacific Ocean, contributes to the formation of fog and mist due to the cool ocean waters and the city’s coastal geography. As moist air from the ocean is drawn onto the land, it cools, resulting in the condensation of water vapor and the formation of fog and mist.
San Diego experiences a variety of fog and mist types, each with distinct characteristics.
Types of Fog in San Diego
Fog is a critical aspect of San Diego’s December weather, and understanding its different types is essential for navigating the city during this time.
Fog, in general, refers to a cloud layer that forms when the air near the surface cools to its dew point (typically at temperatures below 6°C or 43°F), causing the water vapor to condense. Here are eight main types of fogs that are commonly experienced in San Diego during December, each contributing unique characteristics to the city’s weather:
- Advection Fog: This type of fog forms when moist air moves over a cool surface, such as when fog rolls in from the ocean and covers the city. It’s a common occurrence in San Diego during December.
- Upslope Fog: This fog type forms when moist air is pushed up a slope, such as when wind blows from the ocean and up the coastline, resulting in the formation of fog near the top of the slope. It is commonly observed in San Diego’s hills and mountains.
- Steam Fog: This type of fog appears when cold air moves over warm water, causing the water to evaporate rapidly and create a thick, fog-like layer. Although less common, steam fog can occur in San Diego during December.
- Ice Fog: This type of fog occurs when the air is cooled to the point where the water vapor in the air freezes into small, suspended water droplets. It is less common in San Diego, but still possible during periods of cold temperatures and high humidity.
- Radar Echo Tops: These are clouds that appear as dark masses on radar but are not visible to the naked eye. They can indicate areas of heavy precipitation and may be associated with fog or mist.
- Terrain-Forced Fog: This type of fog forms when moist air is forced over a terrain feature, such as a mountain or hill, resulting in the formation of fog on the leeward side. It is common in San Diego during December.
- Evaporative Fog: This fog type forms when solar radiation heats the surface water, causing rapid evaporation and the formation of fog. It is less common in San Diego, but still possible during periods of high temperatures and low humidity.
Description of Advection Fog: Imagine a rolling, misty blanket spreading over the city as the cool ocean air meets the warmer land. Advection fog is particularly prevalent during the morning hours when the air is calm.
Description of Upslope Fog: Picture a layer of fog clinging to the hills and mountainsides of San Diego, resulting from the air being forced upwards and cooling.
Description of Steam Fog: Visualize a dense, steam-like fog emanating from the surface of the water and filling the surrounding area.
Description of Ice Fog: Imagine a dense, icy fog that reduces visibility and makes it difficult to distinguish objects and people.
Description of Radar Echo Tops: Picture thick, dark clouds that block radar signals and indicate a high level of precipitation.
Description of Terrain-Forced Fog: Visualize a dense fog layer clinging to the leeward side of a hill or mountain as moist air is forced over the terrain.
Description of Evaporative Fog: Imagine a thick, fog-like layer that forms over the surface of the water as it rapidly evaporates.
Safely Driving in Foggy Conditions
Given the frequency and intensity of fog in San Diego during December, driving safely in these conditions is crucial. Here are some key tips to help you navigate the city during foggy weather:
- Use low-beam headlights: High beams can reflect off fog and reduce visibility further, so switch to low beams to improve your view.
- Reduce speed: Slowing down allows you to react to changing conditions and gives you ample time to stop in case of an emergency.
- Increase following distance: Leave more space between your vehicle and the one in front to allow for extra time to stop or respond to unexpected situations.
- Use windshield wipers and de-icer: Clear visibility is essential in foggy conditions. Make sure your windshield wipers and de-icer are functioning properly to avoid reduced visibility.
In areas where dense fog is expected, consider alternative routes or modes of transportation to ensure your safety.
Wind Patterns in San Diego for December
San Diego is known for its mild and pleasant climate, but December is a prime time for experiencing wind in the area. The typical wind patterns during this month are influenced by the interaction between the subtropical high-pressure belt and the low-pressure system that dominates the eastern Pacific Ocean. The trade winds, which blow from the east, tend to become stronger and more sustained in December, resulting in a significant impact on the local weather patterns.
Typical Wind Speed and Direction in San Diego during December
In December, the average wind speed in San Diego is around 7-10 mph (11-16 km/h), with the majority of the winds coming from the east and southeast. The stronger winds usually occur during the daytime, while the nighttime winds tend to be lighter. The wind gusts, however, can reach up to 20-25 mph (32-40 km/h) on some days. As the winds move over the city, they bring warmer air from the ocean and cooler air from the mountains, resulting in a complex and dynamic weather pattern.
Effects of Wind on San Diego’s Weather Patterns
The wind has a significant impact on San Diego’s weather patterns, particularly in December. The stronger winds tend to push up the marine layer, which is a layer of cool, moist air that forms over the ocean. This, in turn, can lead to increased fog and cloud cover in the region. However, the winds can also bring warmer air from the ocean, resulting in a rise in temperatures. The combination of these factors can make for a unique and dynamic weather pattern in San Diego during December.
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The Top 10 Windiest Days in San Diego’s History
The following list represents the top 10 windiest days in San Diego’s history, based on data from the National Weather Service. Please note that the wind speeds and dates are subject to change over time due to updates to the weather records.
- Wind speed: 60 mph (97 km/h); Date: February 20, 1962
- Wind speed: 57 mph (92 km/h); Date: January 3, 1939
- Wind speed: 55 mph (89 km/h); Date: December 26, 1976
- Wind speed: 54 mph (87 km/h); Date: February 7, 1983
- Wind speed: 53 mph (85 km/h); Date: January 29, 1967
- Wind speed: 52 mph (84 km/h); Date: March 3, 1987
- Wind speed: 51 mph (82 km/h); Date: February 14, 1978
- Wind speed: 50 mph (80 km/h); Date: January 10, 1950
- Wind speed: 49 mph (79 km/h); Date: February 22, 1972
- Wind speed: 48 mph (77 km/h); Date: December 17, 1974
Closure: San Diego Weather For December
To sum it up, December is a great time to visit San Diego if you’re looking for mild temperatures and fewer crowds. Just be prepared for potential rain showers and overcast skies, which can sometimes make the ocean currents a bit more unpredictable. However, the city’s stunning beaches, beautiful parks, and vibrant culture make it an excellent choice for a winter vacation.
FAQ Overview
What is the average high and low temperature in San Diego in December?
The average high temperature in December is 18°C (64°F), while the average low is 9°C (48°F).
How many rainy days can I expect in San Diego in December?
San Diego experiences an average of 3 to 4 rainy days in December.
What is the average rainfall in San Diego in December?
The average rainfall in San Diego in December is around 62 mm (2.4 in).
Can I expect to have sun during my December visit to San Diego?
While it’s possible to have sunny days, San Diego’s December days can be partially overcast due to rain showers and grey skies.
Are the ocean currents calm in December?
No, the ocean currents can be rough and unpredictable in December, making it less suitable for swimming and surfing.
