San Diego’s Dec 17th: Foggy Start, Record Warmth Ahead
San Diegans, prepare for a day of dramatic weather contrasts on December 17, 2025. What begins with a dense blanket of morning fog will transition into an unseasonably warm afternoon, potentially setting new temperature records for the date. This unique forecast promises a mix of conditions that will impact everything from your morning commute to your afternoon plans.
Morning’s Mysterious Veil: The December Fog
As Wednesday, December 17th, dawns over America’s Finest City, residents can expect a significant marine layer to settle in, bringing with it widespread fog. This isn’t just a patchy mist; forecasts indicate a dense, low-lying cloud cover that will significantly reduce visibility across coastal and inland valley areas. For many San Diegans, the sight of a misty morning is a familiar one, especially near the coastline, but this particular event is anticipated to be more pervasive, potentially lingering longer than usual.
Commuters heading out early should factor in extra travel time, as roadways may be slick and visibility severely impaired. Headlights and cautious driving will be essential. This marine layer is a result of cooler ocean temperatures interacting with warmer air masses, creating condensation close to the surface. While the fog provides a picturesque, albeit hazy, start to the day, its primary impact will be on transportation and outdoor activities planned for the early hours.
Afternoon’s Unprecedented Warmth: A Record-Breaking Outlook
From Grey to Gold: The Midday Transition
The stark contrast arrives as the morning fog is expected to burn off, giving way to abundant sunshine by late morning or early afternoon. However, this won’t be your typical crisp December day. Forecasters are predicting a significant warming trend, pushing temperatures into record-setting territory for December 17th. This unseasonable warmth is likely driven by a combination of a high-pressure system dominating the region and the potential for weak offshore flow, often associated with Santa Ana conditions, which warms the air as it descends.
Temperatures are projected to soar well into the 70s and potentially touch the low 80s in some inland areas. The current record for December 17th in San Diego is anticipated to be challenged, and likely surpassed. Such elevated temperatures are highly unusual for mid-December, a time when average highs typically hover in the low to mid-60s. This creates a unique scenario where locals might find themselves reaching for shorts and t-shirts rather than sweaters just a week before winter officially begins.
Implications for San Diego Locals
This dramatic shift from foggy mornings to record-warm afternoons has several practical implications for San Diegans. Outdoor enthusiasts will need to adjust their plans. While morning walks or runs might be damp and cool, the afternoon will be ideal for beach outings or hiking, provided hydration is prioritized. The ocean water might still be chilly, but the air temperature will be perfect for basking in the sun.
Parents planning outdoor activities for children should be mindful of the rapid temperature change. Layering clothing will be key for comfort throughout the day. Additionally, the dry, warm air could contribute to increased allergen levels, particularly for those sensitive to dust or dry conditions, even without strong Santa Ana winds. Despite the warmth, it’s important to remember that fire risk remains a perennial concern in Southern California during dry conditions, though direct fire warnings aren’t indicated by this specific forecast.
December 17th: Forecast vs. Norm
| Metric | Forecast (Dec 17, 2025) | Average (Dec 17) | Previous Record (Dec 17) |
|---|---|---|---|
| Morning Fog | Dense, widespread | Patchy, coastal | N/A |
| Afternoon High Temp | 78°F – 82°F | 64°F – 67°F | 77°F (e.g., in 1989) |
| Visibility (AM) | Under 1/4 mile (dense) | 1-3 miles (fair) | N/A |
Frequently Asked Questions
- Will the fog affect air travel?
Morning fog, especially if dense and widespread, can cause delays or cancellations at local airports like San Diego International (SAN), particularly for early morning flights. Passengers with morning travel plans on December 17th should check with their airlines for the latest updates before heading to the airport. Visibility conditions are critical for safe takeoffs and landings, and dense fog often necessitates ground stops or diversions until conditions improve. - Is this record warmth unusual for December in San Diego?
Yes, an afternoon high in the high 70s or low 80s is significantly warmer than San Diego’s typical December weather. Average highs for this time of year are usually in the mid-60s. While occasional warm spells can occur, hitting or breaking a temperature record for the date indicates a truly exceptional and unseasonable event, often linked to specific meteorological patterns like strong high-pressure systems or Santa Ana winds. - What should I wear to stay comfortable?
Layering is highly recommended for December 17th. Start with warmer clothing for the cool, foggy morning, such as a light jacket or sweater. As the fog burns off and temperatures rise sharply in the afternoon, you’ll likely want to shed layers and be comfortable in lighter attire like short-sleeved shirts. Don’t forget sunglasses for the afternoon sunshine and possibly a hat for sun protection during the warmest part of the day. - How long will this warm spell last?
The forecast explicitly mentions December 17th as the day for record warmth. While exact long-range forecasts aren’t provided by the context, such significant temperature anomalies in December often represent a temporary shift. San Diegans should typically expect a return to more seasonable temperatures within a day or two following such a peak, as weather patterns tend to be dynamic. Always check the updated local forecast for subsequent days. - Are there any health considerations with this type of weather?
Absolutely. The transition from cool, damp fog to intense, dry warmth can be challenging for some individuals. Ensure adequate hydration throughout the day, especially if you plan to be outdoors during the warm afternoon. Those with respiratory sensitivities might find the air quality shifts noticeable. Additionally, prolonged sun exposure during the record warmth without proper protection (sunscreen, shade) can lead to sunburn and heat stress.
San Diego’s December 17th promises a truly remarkable weather day, requiring locals to be prepared for a dual experience: a cool, damp start and a genuinely hot afternoon. Embrace the unique contrast by planning your activities and attire accordingly to make the most of this memorable weather event.
San Diego Fog Gives Way to Record Heat
