Monterrey has a semi-arid climate . It is one of the warmest major cities in Mexico. Summers are generally hot, spring and fall temperate, and winters mild, with temperatures rarely below freezing. The average high in August is 35 °C (95 °F) and the average low is 23 °C (73 °F). The average January high is 21 °C (70 °F) and the average low in January is 8 °C (46 °F). Rainfall is scarce in winter, but more frequent during May through September.
Monterrey frequently experiences extreme weather changes; for example, it sometimes reaches 30 °C (86 °F) in January and February, the coldest months. The most extreme weather changes in summer occur with rainfall, which can reduce temperatures significantly, and the temporary absence of the northern winds in winter, which can lead to abnormally high temperatures. Seasons are not well defined; the warm season may start in February and may last until September. In April and May 2011 temperatures reached 45 °C (113 °F) or higher, causing fires and extreme heat. Snow is a very rare event, although an accumulation of 50 cm (20 inches) in 8 hours occurred in January 1967. The most recent snowfall was on February 2021, Sleet and ice events occurred in January 2007, December 2009, January and February 2010 and February 2011, caused by temperatures around −5 °C (23 °F).
From June 30 to July 2, 2010, Monterrey was hit by the worst natural disaster in the city’s history when Hurricane Alex delivered more than 584 millimetres (23 in) of rain in 72 hours, with areas reaching up to 1 metre (39 in) of rain during that same period, destroying homes, avenues, highways and infrastructure, and leaving up to 200,000 families without water for a week or more. The amount of water that fell was equivalent to the average precipitation for a year. This was about 3–4 times as much rain as Hurricane Gilbert produced in the city on September 15, 1988. The death toll of Hurricane Alex was estimated to be around 20.