Climate Barra Rio de Janeiro
Rio has a tropical savanna climate that closely borders a tropical monsoon climate according to the Köppen climate classification, and is often characterized by long periods of heavy rain from December to March. In inland areas of the city, temperatures above 40 °C (104 °F) are common during the summer, though rarely for long periods, while maximum temperatures above 27 °C (81 °F) can occur on a monthly basis.
Along the coast, the breeze, blowing alternately onshore and offshore, moderates the temperature. Because of its geographic situation, the city is often reached, especially during autumn and winter, by cold fronts advancing from Antarctica, causing frequent weather changes. It is mostly in summer that strong showers provoke catastrophic floods and landslides. The mountainous areas register greater rainfall since they constitute a barrier to the humid wind that comes from the Atlantic.
It is said that the city had frosting sometime in its past, but it was never confirmed. Some areas within Rio de Janeiro state have snow grains and ice pellets with an even frequency (popularly called granizo, or 'hail', although it is in fact melted and refrozen snow falling in the form of a ball – true hail and graupel are much less common). These phenomena are definitely not rare or limited to a few regions, happening in the metropolitan area (including western suburbs of the city itself) at least one time in the 21st century, said to be approximately each two decades or less in some regions. In other areas there is true snowfall more than once in each century, most commonly in the cities of Resende and Itatiaia (in lower latitudes than Rio de Janeiro, but much higher altitudes), nation's coldest ones outside Southern Brazil, and the most propitious to frosting.
Roughly in the same suburbs corresponding to the March 2012 granizo fall (Nova Iguaçu–Campo Grande), there was a tornado-like phenomena in January 2011, for the first time in the region's recorded history, causing structural damage and lasting blackouts, but no fatalities. The World Meteorological Organization alerts Brazil, specially its Southeastern region, that events as the catastrophic January 2011 Rio de Janeiro floods and mudslides are not an isolated phenomena and that Brazil must be prepared for severe weather in the next years. "This (the early 2010s serial devastation in Rio de Janeiro's mesoregions Metropolitana do Rio de Janeiro and Sul Fluminense) was not an isolated event. The events in Brazil confirms a global trend that storms tend to be increasingly strong and in places where it did not take place with the same force", said Rupakumar Kolli, WMO expert on climatological phenomena.
The average annual minimum temperature is 21 °C (70 °F), the average annual maximum temperature is 27 °C (81 °F), and the average annual temperature is 23 °C (73 °F). The average yearly precipitation is 1,175 mm. According to INMET, the minimum temperature recorded was 4.8 °C (41 °F) in July 1928, in the Campo dos Afonsos bairro (the Portuguese word for neighbourhood), and the absolute maximum was 44 °C (111 °F) in February. The lowest temperature ever registered in the 21st century was 8.1 °C (47 °F) in Vila Militar, July 2011. Temperatures below 10 °C (50 °F) are very rare in the city. The temperature varies according to elevation, distance from the coast, and type of vegetation. Winter brings mild temperatures and less rain than in the summer.
Average annual temperature of the sea is 23–24 °C (73–75 °F), from 22 °C (72 °F) in the period July–October to 26 °C (79 °F) in February and March. The wettest and driest months tend to be December and August respectively.