occasions, provoked catastrophic floods and landslides. The mountainous areas register greater rainfall since they constitute a barrier to the humid wind that comes from the Atlantic. The city has had rare frosts in the past. Some areas within Rio de Janeiro state occasionally have falls of snow grains and ice pellets (popularly called ) and hail. Drought is very rare, albeit bound to happen occasionally given the city's strongly seasonal tropical climate. The Brazilian drought of 2014–2015, most severe in the Southeast Region and the worst in decades, affected the entire metropolitan region's water supply (a diversion from the Paraíba do Sul River to the Guandu River is a major source for the state's most populous mesoregion). There were plans to divert the Paraíba do Sul to the Sistema Cantareira (Cantareira system) during the water crisis of 2014 in order to help the critically drought-stricken Greater São Paulo area. However, availability of sufficient rainfall to supply tap water to both metropolitan areas in the future is merely speculative. Roughly in the same suburbs (Nova Iguaçu and surrounding areas, including parts of Campo Grande and Bangu) that correspond to the location of the March 2012, February–March 2013 and January 2015 pseudo-hail (granizo) falls, there was a tornado-like phenomenon in January 2011, for the first time in the region's recorded history, causing structural damage and long-lasting blackouts, but no fatalities. The World Meteorological Organization has advised that Brazil, especially its southeastern region, must be prepared for increasingly severe weather occurrences in the near future, since events such as the catastrophic January 2011 Rio de Janeiro floods and mudslides are not an isolated phenomenon. In early May 2013, winds registering above caused blackouts in 15 neighborhoods of the city and three surrounding municipalities, and killed one person. Rio saw similarly high winds (about ) in January 2015. The average annual minimum temperature is , the average annual maximum temperature is , and the average annual temperature is . The average yearly precipitation is . Temperature also varies according to elevation, distance from the coast, and type of vegetation or land use. During the winter, cold fronts and dawn/morning sea breezes bring mild temperatures; cold fronts, the Intertropical Convergence Zone (in the form of winds from the Amazon Forest), the strongest sea-borne winds (often from an extratropical cyclone) and summer evapotranspiration bring showers or storms. Thus the monsoon-like climate has dry and mild winters