December 2026 Will Be the Hottest December on Record in the United States: 68% Probability
As meteorological indicators converge, a significant warming trend is emerging for the end of 2026. Current data suggests there is a 68% probability that December 2026 will be the warmest December on record for the contiguous United States. To achieve this, the average temperature must exceed the existing benchmark of 39.3°F, which was established in December 2021. This forecast is supported by several overlapping climate drivers, including oceanic oscillations and a rising thermal baseline across the continent.
The Driving Force of El Niño
One of the most critical factors in this prediction is the state of the Pacific Ocean. There is an 88% to 94% probability that El Niño will be the dominant climate driver from mid-2026 through February 2027. Typically, El Niño shifts the Pacific jet stream southward, a phenomenon that frequently results in warmer and drier conditions across the northern United States. Even if the event is characterized as 'weak'—with a projected magnitude of approximately 0.84°C—it can still provide a substantial nudge toward record-breaking warmth when synchronized with other factors.
Oceanic Synergy and Regional Warming
The potential for extreme heat is further amplified by the Atlantic Multidecadal Oscillation (AMO), which is currently in a positive or warm phase. This phase can influence North American temperature patterns and enhance overall warming signals. Additionally, the Pacific Decadal Oscillation (PDO) has remained in a negative state since 2020, reaching its most extreme negative values since 1955. The combination of a warm AMO and a negative PDO creates an atmospheric setup that often favors warmer winter months in many parts of the U.S.
Accelerated Winter Trends
Adding to the momentum is the fact that meteorological winter is the fastest-warming season for much of the United States. Regions such as the Northeast and Great Lakes are seeing rapid temperature increases, with some cities like Chicago, Cleveland, and Detroit projected to see winter lows increase by as much as 5.5°F. Because these high-latitude regions are warming so quickly, any significant warm spike in December could heavily influence the contiguous U.S. average, pushing it past the critical 39.3°F threshold.
Assessing Uncertainty and Model Limitations
While the indicators strongly favor warmth, the probability is not higher due to inherent meteorological volatility. A single major Arctic outbreak or 'Polar Vortex' event could temporarily drop temperatures and prevent a record from being set. Furthermore, the 2021 benchmark is exceptionally high, sitting 6.7°F above normal. However, it is important to note that historical data suggests climate models may underestimate extreme temperature anomalies by 11% to 12%, suggesting that the actual physical reality could be even more intense than current projections indicate.
