A strong solar flare measuring M8.1 erupted from Active Region 4299 at 20:39 UTC on December 6, 2025. The event started at 20:29 and ended at 20:49 UTC. A full-halo coronal mass ejection was produced, with impact expected early to midday on December 9, potentially causing periods of G3 – Strong geomagnetic storming.
A major atmospheric river (AR4–AR5 possible) is forecast to make landfall over the Pacific Northwest early Monday, December 8, 2025, and persist through Wednesday, December 10, bringing multiple days of heavy rain and elevated snow levels. Ensemble guidance shows ~70–80% of members reaching at least AR4 in southern coastal Washington, with ~20–30% indicating AR5, raising the risk of widespread riverine flooding.
Three atmospheric rivers (ARs) are forecast to make landfall over the Pacific Northwest (PNW) through December 10, 2025, producing prolonged precipitation and high moisture transport across western Washington and Oregon.
The polar vortex is forecast to settle near Hudson Bay, sending repeated waves of Arctic air into the central and eastern U.S. during the first half of December 2025.
The season’s first nor’easter began impacting the Mid-Atlantic and Northeast overnight, prompting a State of Emergency in parts of New Jersey and school closures across multiple states. The storm is forecast to rapidly intensify, possibly dropping up to 30 cm (12 inches) of snow across parts of the interior Northeast through Tuesday.
Over 1 000 people have died and hundreds remain missing on Tuesday, December 2, 2025, after rare Tropical Cyclone Senyar brought severe flooding and landslides across Indonesia, Thailand, and Malaysia.
NOAA’s Space Weather Prediction Center (SWPC) issued a G2 – Moderate geomagnetic storm watch for December 3 and 4, 2025, following a coronal mass ejection (CME) associated with the X1.9 solar flare from Active Region 4299 on December 1. The CME is expected to deliver a glancing blow to Earth’s magnetic field, coinciding with a co-rotating interaction region (CIR) and a sector boundary crossing, increasing the potential for moderate geomagnetic storming and visible auroras at mid-latitudes.
The first nor’easter of the season is forecast to rapidly intensify by Wednesday, December 3, 2025, bringing 25–38 cm (10–15 inches) of snow, violent winds, and whiteout conditions across parts of the U.S. Northeast and Nova Scotia, and Newfoundland, Canada.
A major solar flare registered as X1.9 erupted from Active Region 4299 at 02:49 UTC on December 1, 2025. The event started at 02:27 and ended at 03:05 UTC. This region is currently making its second run through the Earth-side of the Sun, after producing multiple X-class flares in early November.
A large chain-reaction crash involving about 45 vehicles occurred on Interstate 70 westbound near Terre Haute, Indiana, at around 10:00 LT on November 29, 2025, amid heavy snowfall and reduced visibility. The collision blocked all westbound lanes for nearly 6 hours, but authorities reported no fatalities or major injuries. The event happened as a winter storm system brought snow and freezing rain across parts of Illinois and Indiana, creating hazardous travel conditions.
