Rio’s average temperature, for example, is around 27ºC (80º F) which climbs to 40ºC, the low hundreds, during the summer months that stretch from December through to March. In the middle of winter, July, the temperatures in Rio can drop as low as 18ºC (65ºF) during the day!
               North of Rio, the weather becomes noticeable more tropical while to the south it can get quite cool, even cold, during the winter months.

Climate

Annual Temperatures
               Although 90% of the country is within the tropical zone, more than 60% of the population lives in areas where altitude, sea winds, or cold polar fronts moderate the temperature. There are five climatic regions in Brazil: equatorial, tropical, semi-arid, highland tropical and subtropical.
               Plateau cities such as São Paulo, Brasília and Belo Horizonte have very mild climates averaging 19°C (66°F). Rio de Janeiro, Recife and Salvador on the coast have warm climates balanced by the constancy of the Trade Winds. In the southern Brazilian cities of Porto Alegre and Curitiba, the subtropical climate is similar to parts of the US and Europe. In this region temperatures in winter can fall below freezing.
               Despite the popular image of the Amazon as a region of blistering heat, temperatures of more than 32°C (90°F) are rarely experienced there. In fact, the annual average temperature in the Amazon region is in the range of 22°C to 26°C (72-79°F), with only a very small seasonal variation between the warmest and the coldest months. The hottest part of Brazil is the northeast where, during the dry season, between May and November, temperatures of more than 38°C (100°F) are recorded frequently. The northeast has greater seasonal variation in temperatures than does the Amazon region. Along the Atlantic coast from Recife to Rio de Janeiro, mean temperatures range from 23°C to 27°C (73°F-81°F). Inland, on higher ground, temperatures are lower, ranging from 18°C to 21°C (64°F-70°F). South of Rio, the seasons are more noticeable and the annual range of temperature greater. The average temperature for this part of the country is in the range between 17°C to 19°C (63°F-66°F).

Annual Rainfall
                Brazil's most intense rainfall is found around the mouth of the Amazon River near the city of Belém, and also in the vast upper regions of Amazonia where more than 2,000 millimetres (78 inches) of rain falls every year. Another important region of heavy rainfall is along the edge of the great escarpment in the state of São Paulo. Most of Brazil, however, has moderate rainfall of between 1,000 to 1,500 millimetres (39 to 59 inches) a year, with most of the rain falling in the summer, between December and April.
               In this region rainfall is undependable and the evaporation rate is very high, making it difficult to raise crops. Along the coastline, south from Recife, the mountains trigger rainfall from the Trade Winds. In some places behind the mountains, such as the region south of Salvador, the hinterland is dry because the rain is dumped on the mountains leaving very little for the area behind.

The Seasons

Seasons in Brazil are the reverse of those in Europe and the United States:

Spring    : 22nd September - 21st December
Summer : 22nd December - 21st March
Autumn  : 22nd March - 21st June
Winter   : 22nd June - 21st September