Christmas season 2025 in the United States: exceptionally warm conditions expected
The Christmas season in 2025 is expected to feature significantly above-average temperatures across much of the United States. According to the latest numerical model outputs, a large upper-level high-pressure system is expected to develop over a vast area of the U.S., allowing the advection of warm air while suppressing cloud formation and precipitation. Daily maximum temperatures in the southern and central U.S. are expected to reach values typical of late spring (Fig. 1; see map ). In some areas, particularly in the central U.S., temperatures are expected to exceed the long-term average by more than 20 °C (≈36 °F). Christmas Day is anticipated to rank among the warmest on record in multiple regions.
The primary cause of these substantially above-average temperatures is the development of an upper-level blocking high. A ridge of high pressure is advancing over the U.S. from the subtropics in the southwest (Fig. 2; see map) and is expected to stabilize over the U.S. in the following days, gradually developing into a persistent upper-level high-pressure system.
Figure 3 (see map) illustrates the forecast distribution of upper-level pressure systems on Wednesday, 24 December 2025, with a significant high-pressure system located over the U.S. This high is expected to induce above-average temperatures through several mechanisms. First, warm air is advected from the south. Second, slow downward motion of air, or subsidence, increases temperature adiabatically. Subsidence reduces relative humidity, dissipates existing clouds, and suppresses further cloud development. This process increases the amount of solar radiation reaching the surface, further enhancing surface warming.
The synoptic pattern in Fig. 3 corresponds to an omega block, a specific type of atmospheric blocking in the mid-latitudes. In this configuration, an upper-level high or pronounced ridge of high pressure is flanked by two low-pressure areas, specifically over the western and eastern U.S. The arrangement of the upper-level pressure systems resembles the Greek letter Ω. Omega blocks significantly slow zonal flow, producing several days to a week of persistent, stable, anomalously warm conditions with minimal precipitation.
Above-average temperatures, particularly in the southern and central U.S., are expected to continue through the end of December. Figure 4 presents an ensemble forecast, illustrating the evolution of 850 hPa air temperatures (~1.5 km) and precipitation from early January 2026 in Kansas City. Temperatures at 1.5 km altitude are used to minimize surface influences, such as diurnal heating and cooling. The red line indicates the long-term average, revealing that December temperatures (green or white lines) are forecasted to be strongly above normal, with anomalies approaching +20 °C. The warm period is expected to terminate with rapid cooling at the end of December (see map).
