Phoenix winter heat rose due to La Niña and climate change.

Phoenix experienced consecutive record-warm winter days around Feb. 27–March 1, and experts attribute the stretch to a combination of La Niña conditions and long-term climate warming.

Phoenix saw an unusually warm meteorological winter that ended with several consecutive days in the 90s. Records were tied or broken on Feb. 27 and Feb. 28, and a 93°F high on March 1 also set a daily record. Meteorologists and climate scientists say the pattern reflects both La Niña conditions and ongoing regional warming. The season’s warmth is part of a longer trend of warmer winters in the region. Key observations: - Phoenix recorded consecutive 90°F days at the end of February and on March 1, with highs reported at 92°F on Feb. 27 and Feb. 28 and 93°F on March 1. - Experts quoted in reporting state the heat resulted from a mix of La Niña-driven drier conditions and persistent climate warming, with many recent warm winters occurring since 2000. - Warmer winter temperatures reduced mountain snowpack and can strain river and reservoir supplies in the Colorado River basin, with forecasts noting lower runoff prospects for places such as Lake Powell. - NOAA scientists reported that La Niña could transition toward neutral conditions through April, leaving seasonal runoff and water supply outcomes uncertain. Summary: The warm winter in Phoenix combined short-term La Niña influences with longer-term warming trends, producing multiple record-high winter days and reducing snowpack that helps feed regional water supplies. Seasonal forecasts may shift as La Niña weakens, and the outlook for runoff and reservoir levels is undetermined at this time.