for example, it sometimes reaches 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 or higher, causing fires and extreme heat. Snow is a very rare event, although an accumulation of in 8 hours occurred in January 1967. The most recent snowfall was in February 2021, Sleet and ice events occurred in January 2007, December 2009, January and February 2010 and February 2011, caused by temperatures around . 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 of rain in 72 hours, with areas reaching up to 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. Demographics According to the national INEGI population census of 2010, of the total population of the state of Nuevo León, 87.3% lived in the Monterrey metropolitan area. The Monterrey metropolitan area is the second most populous in Mexico with more than 5 million. It comprises the municipalities of Monterrey, Apodaca, Escobedo, García, Guadalupe, Santiago, Juárez, San Nicolás de los Garza, San Pedro Garza García, Santa Catarina and Salinas Victoria. Education Monterrey has an estimated 3.7% rate of illiteracy. In 2005, of an estimated 983,359 inhabitants above 6 years of age, 36,689 were illiterate. In 2005, the city had 72 public libraries, with 298,207 books available, serving an estimated 478,047 readers. The Universidad Autónoma de Nuevo León (Autonomous University of Nuevo León, UANL) is the third-largest Mexican university and is ranked by the Reader's Digest-AC Nielsen Survey 2005 as the top public university in northeast Mexico. Its main campus, Ciudad Universitaria (University City), covers approximately . The UANL system comprises 26 colleges (faculties), 22 graduate divisions, 24 high schools, 1 center of bilingual