Weather Los Angeles California December: Average Temperatures, Rainfall, and What to Expect

December in Los Angeles presents a mild departure from the intense summer heat, characterized by comfortably cool days, increased cloud cover, and the beginning of the rainy season. This month typically offers daytime temperatures in the mid-60s Fahrenheit, with lower humidity and significantly reduced sunshine hours compared to summer. Understanding the historical patterns and current forecasting parameters is essential for residents planning outdoor activities and visitors adjusting their itineraries.

Typical Temperature Ranges and Historical Averages

Los Angeles experiences a Mediterranean climate, and December serves as a clear transition into winter conditions. While frost is exceptionally rare at sea level, the mercury frequently dips into the 40s and 50s Fahrenheit during nighttime and early morning hours. Daytime highs usually stabilize in the upper 60s, creating a significant temperature swing between dawn and afternoon.

The following data points represent long-term averages for Los Angeles Downtown during the month of December:

• Average High Temperature: 68°F (20°C)
• Average Low Temperature: 49°F (9°C)
• Average Rainfall: 3.5 inches (89 mm)
• Average Humidity: 65%

"December marks the point where we definitively leave the dry season behind," explains Dr. Arlena Jones, a climatologist at the University of Southern California. "The shift is dramatic in terms of daylight and atmospheric river potential, though the actual cold is more relative than extreme by national standards."

Rainfall and Precipitation Patterns

December is a critical month for Los Angeles's water supply, as it is one of the primary months for the region's annual precipitation. The majority of the rain falls through a series of intense atmospheric river events, which are long corridors of concentrated moisture in the atmosphere. These systems can deliver torrential rain in short periods, followed by several days of dry conditions.

Historically, December accounts for a significant portion of the city's total annual rainfall. While the rain is vital for replenishing reservoirs, it can also lead to hazardous driving conditions and localized flooding in areas with poor drainage.

1. Onset: Rainfall usually increases steadily throughout the month, with the first significant storms often arriving mid-to-late December.
2. Intensity: Los Angeles typically experiences 4 to 6 days of measurable precipitation in December, though not all days are consecutive.
3. Impact: Rain events are generally short-lived but can be intense, leading to a shift in outdoor recreation toward indoor venues or covered spaces.

Sunshine, Cloud Cover, and Daylight

The persistent marine layer, often referred to as "May Gray" or "June Gloom," can sometimes linger into December, particularly in coastal areas and the Los Angeles Basin. This layer of cool, moist air creates a gray overcast that blocks direct sunlight and keeps daytime temperatures lower than they would be otherwise.

Compared to the summer months, where the sun dominates the sky for over 12 hours, December days are significantly shorter. The winter solstice occurs on December 21 or 22, marking the shortest day of the year. In Los Angeles, this translates to approximately 10 hours of daylight, with sunrise around 6:45 AM and sunset around 4:45 PM.

• Average Sunny Days: 6 to 7 days
• Average Cloudy Days: 15 to 20 days
• Average Daylight Duration: ~10 hours

Ocean Temperatures and Coastal Influence

The Pacific Ocean plays a dominant role in dictating Los Angeles weather, even in winter. The water temperature remains relatively cool year-round, hovering in the high 50s to low 60s Fahrenheit. This cool water keeps the coastal air temperatures moderated but does not prevent the chill felt on exposed skin, especially in the evenings.

Surf conditions are often robust during December, attracting experienced surfers to the beaches. Winter storms generate powerful swells that create ideal surfing conditions, though the water is too cold for extended swimming without a wetsuit.

What to Wear and Outdoor Activity Planning

Dressing for Los Angeles in December requires a strategic layering approach. The temperature differential between a shaded morning and a sunny afternoon can be 15 to 20 degrees.

Recommended attire includes:

• Base Layers: Light sweaters or thermal tops.
• Mid Layers: Fleece jackets or light wool sweaters.
• Outerwear: A waterproof or water-resistant jacket is highly recommended to guard against sudden rain showers.
• Accessories: Sunglasses are useful on clear days, but a compact umbrella is a practical accessory for commutes.

Outdoor activities such as hiking in Griffith Park or Santa Monica Mountains remain popular, but it is wise to check for trail closures due to mudslides, which can occur after heavy rain. Indoor alternatives, such as museum visits or gallery hopping, become more appealing during periods of heavy rain or high surf advisories.

Microclimates and Regional Variations

It is crucial to note that "Los Angeles weather" is not a monolithic entity. The city's geography, featuring mountains and basins, creates distinct microclimates that residents must navigate.

While downtown might be experiencing a rainy, 60-degree day, the neighborhoods of Beverly Hills or the Westside might enjoy the same conditions. Conversely, the valleys, such as San Fernando or San Gabriel, can be significantly cooler and may experience frost on rare mornings.

• Coastal Areas (Santa Monica, Venice): Cooler temperatures, higher humidity, and more frequent cloud cover.
• Inland Valleys (Burbank, Glendale): Greater temperature variance, cooler nights, and increased fog potential.
• Mountain Regions (Hollywood Hills, Beverly Hills): Similar to coastal but often clearer and sunnier than the basins.

Travel and Event Considerations

For those visiting Los Angeles during December, the holiday season is in full swing. The weather supports traditional outdoor holiday markets and light displays, though attendees should be prepared for cooler temperatures and the possibility of rain.

Major events, such as parades or outdoor concerts, will proceed rain or shine, so checking the forecast in the days leading up to the event is standard practice. Airlines and hotels remain busy, but the weather rarely causes the widespread flight cancellations seen in northern cities.

Ultimately, December in Los Angeles offers a unique blend of winter ambiance and Californian warmth. It is a month of transition, where the frantic energy of summer gives way to a more contemplative, rain-kissed landscape perfect for enjoying the city’s indoor cultural offerings or braving the elements for a rare sunny afternoon.