Wahiawa Dam on Oʻahu, Hawaii, was placed under an imminent failure risk alert on March 20, 2026, prompting emergency evacuations in downstream communities, including Haleiwa and Waialua.
Life-threatening flash flooding struck Oʻahu’s North Shore, Hawaii, on March 20, 2026, after a slow-moving Kona low produced more than 330 mm (13 inches) of rain in parts of northern Oʻahu in about 12 hours from the evening of March 19 into the morning of March 20. Flooding in the Haleiwa and Waialua areas cut off road access, prompted evacuation orders, and triggered emergency response operations.
A historic March heat event affected the U.S. Southwest on March 19 and 20, 2026, setting a new March temperature record in Las Vegas, Nevada, and a new highest March temperature ever recorded in the United States near Martinez Lake, Arizona. Multiple daily and monthly records were also broken across parts of Nevada, California, and Arizona, while authorities in Phoenix closed some hiking trails because of heat risk.
Over USD 3 billion worth of crop losses were reported across Florida due to freeze conditions triggered by winter storms Ezra and Gianna, between December 30, 2025 and February 4, 2026. The freeze affected 66 of the state’s 67 counties and impacted multiple agricultural sectors during peak production periods
A second Kona low is expected to affect the Hawaiian Islands beginning the evening of March 19, 2026, bringing additional rainfall to areas already impacted by record-breaking flooding from a previous storm. A Flood Watch is in effect from 18:00 LT on March 19 through 18:00 LT on March 22 for Maui County, Oʻahu, and Hawaiʻi Island.
A slow-moving Kona low brought extreme rainfall to the Hawaiian Islands between March 10–16, 2026, producing record-breaking totals at multiple long-term stations, particularly on Maui and Oʻahu. Honolulu and Kahului both set new daily rainfall records on March 13, while multi-day accumulations on Maui reached up to about 1 170 mm (46 inches), triggering flooding, landslides, and widespread disruption.
A multi-day atmospheric river event affecting western Washington, United States, since March 15, 2026, is elevating flood potential as cumulative rainfall and snowmelt impact the regional river basins. Prolonged precipitation and high snow levels are leading to rising rivers, with flood risk expected to persist through early March 21.
An anomalously early-season heatwave intensified across the western United States on March 18, 2026, with Extreme Heat Warnings in effect for parts of the Desert Southwest and temperatures forecast to expand east into the Rockies and Great Plains by March 20. Highs are expected to reach 40–44°C (104–112°F) in the hottest desert regions, with numerous daily and some monthly March records likely to be broken.
A late-season blizzard affected northern Michigan between March 15 and 17, 2026, dropping up to 132.1 cm (52 inches) of snow in parts of the Upper Peninsula and breaking snowfall records at the National Weather Service office in Marquette. Governor Gretchen Whitmer declared a state of emergency on March 17 for seven counties in the Upper Peninsula and northern Lower Peninsula as heavy snow, ice, and strong winds disrupted travel and power service.
A stalled atmospheric river over the Pacific Northwest is forecast to deliver 127–254 mm (5–10 inches) of precipitation to parts of Washington between March 17 and 20, 2026. High freezing levels above 2 100 m (7 000 feet) will result in rainfall across most elevations, accelerating snowmelt and increasing the likelihood of riverine flooding.
