Hermosillo, Sonora, the Mexican state capital just south of Phoenix, torched its way past winter heat records this week, topping 100°F on Monday, March 2, 2026, after a late February burst that sent temperatures into the mid 100s. Nogales, Sonora, also logged an unusually hot March 2 reading near 87°F. The out of season heat stretched across much of Sonora, turning what should be mild winter days into full on summer conditions for residents, outdoor workers and local services.
Records across Sonora
On Monday, March 2, temperatures in Hermosillo climbed above 100°F, the hottest March 2 on record for the capital, while a number of other Sonoran cities saw highs in the 90s as border focused reporting tracked the spike. Nogales, Sonora, hit roughly 87°F that same day, according to KJZZ.
Conagua validates February spike
Mexico’s weather agency confirmed that the late February heat was not a fluke. The observatory at Hermosillo’s airport registered about 41°C (about 105.8°F) on Feb. 26, the hottest February day on record for the city, according to El Universal. Local meteorologists told reporters that a persistent heat wave briefly pushed the capital into temperatures that usually show up in summer, not winter.
Why Phoenix readers should pay attention
Phoenix has been running hot too, wrapping up what meteorologists have called the warmest meteorological winter on record, with a stretch of late February and early March days marked by unusually high daytime temperatures and warm nights. That string of records has researchers and water managers taking a hard look at regional snowpack and wildfire risk, as reported by The Arizona Republic.
Large scale drivers: La Niña plus background warming
Experts are pointing to a familiar combination behind the late winter heat. A lingering La Niña pattern, paired with long term warming trends that lift baseline temperatures, helped stack the deck in favor of hotter, drier conditions. The Climate Prediction Center has kept a La Niña advisory in place while calling for a likely shift to ENSO neutral sometime between February and April 2026, a setup that has supported a warmer and drier pattern across the Southwest, according to NOAA's Climate Prediction Center.
Short term outlook and local guidance
Forecasters say the current burst of heat may not last. Weather models and local meteorological services expect a cold front to roll through in early March, with daytime highs dropping into the low 20s °C (around the high 60s to low 70s °F) between March 6 and 10, according to El Imparcial. Authorities are urging people, especially outdoor laborers, older adults and children, to stay hydrated and steer clear of the midday sun while the region rides out these sharp temperature swings.
For Phoenix area readers, the message is that this warm winter is part of a broader pattern on both sides of the border, and that any cool down can arrive fast. Keep tabs on local forecasts from the National Weather Service Phoenix and on updates from Mexican meteorological services covering Hermosillo and the wider Sonora region.
