Comet 3I/ATLAS will make its closest approach to Earth on December 19, 2025, and can be watched via the Virtual Telescope Project live stream, scheduled to start at 04:00 UTC on December 19 (23:00 EST on December 18).
Forecast models suggest that El Niño conditions are likely to develop during 2026, marking a shift from the ongoing weak La Niña. The transition is expected to influence jet stream patterns and temperature anomalies across the United States, Canada, and Europe, potentially reshaping rainfall distribution and winter storm activity in the Northern Hemisphere.
An earthquake swarm that began near downtown San Ramon, California, in October remained active on December 15, with three earthquakes recorded within a few hours by the U.S. Geological Survey. The swarm is occurring in a structurally complex fault zone near the Calaveras Fault, where stress is released through repeated small ruptures rather than a single larger earthquake.
Subseasonal forecasts by CW3E show strong multi-model agreement on above-normal atmospheric river activity across the U.S. West Coast during mid- to late December, with the strongest signals over Northern California. Forecast regime tools indicate a transition from a West Coast Ridge to a Pacific Ridge during this period, altering temperature and precipitation patterns across the region.
Kīlauea’s Halemaʻumaʻu crater, Hawaiʻi, began erupting at 08:45 HST (18:45 UTC) on December 6, 2025, when fountains emerged from the north vent, marking the start of Episode 38 of the ongoing summit eruption. Within minutes, a south vent opened, and by 09:15 HST a rare triple-vent lava fountain was active, producing jets up to 370 m (1 200 ft) high and a 6 km (20 000 feet) plume above the summit. The eruption lasted 12.1 hours, covered more than half of Halemaʻumaʻu crater with new lava, destroyed the USGS V3 streaming camera, and ended abruptly at 20:52 HST on the same day (06:52 UTC on December 7).
UK researchers report that radiation levels at commercial flight altitudes reached their highest values in 20 years following the X5-class solar flare on November 11, 2025, with the resulting Ground Level Enhancement driving single-event upset rates in avionics not seen since 2006.
Ground-based observations on November 16 and 17, 2025 captured multiple jets on the interstellar object 3I/ATLAS, including sunward jets and an extended anti-tail. The images were obtained from telescopes in New Mexico, USA and France. A public online observation by the Virtual Telescope Project is scheduled at 04:15 UTC on November 19, 2025.
High-resolution observations from the Virtual Telescope Project on November 13, 2025, revealed multiple fragments and debris structures in the inner coma of comet C/2025 K1 (ATLAS), confirming a post-perihelion breakup.
An early stratospheric warming developing over the Arctic in late November 2025 is raising the likelihood of colder conditions and increased snowfall across parts of the United States, Canada, and possibly Europe in December.
A strong atmospheric river is forecast to make landfall along the U.S. West Coast on Wednesday, November 12, 2025, bringing heavy rain and mountain snow across much of California through Friday, November 14.
