As the savvy traveler has probably already figured out, Brazil’s weather is as variable as its landscape. The equator bisects the country, and so 90% of the country is tropical. Temperatures along the equator are hot with next to no seasonal variation.
As the fifth largest country in the world, Brazil has a correspondingly wide diversity of climate, ranging from temperate to equatorial. Belem, Macupa, and other northern parts of the country are dominated by equatorial and tropical rainforest weather. Rio de Janeiro has an extremely warm and muggy savannah climate which borders on monsoon tropical. Sao Paulo and points further south have a temperate climate. Snow sometimes falls on the higher mountains, while the southernmost parts of Brazil can expect an occasional frost. Thus, there is no single best time of year to visit Brazil.
Yet most parts of Brazil outside the equatorial region do have seasons, and some of them even come close to having frost during their winters. In general, the busiest and warmest times of year for beaches are December, January, and February, which is high summer in the southern hemisphere. At this time of year, shallow ocean temperatures can be as high as 75 degrees in many places. However, most people from temperate parts of the world will find most major Brazilian beaches comfortable at any time of year.
Belem and the Amazon River basin
The weather in this region of Brazil is predominantly steamy and very stable in temperature. Year-round high temperatures average in the high 80s, while low temperatures almost never go below 70.
As a rainforest region, there is no genuinely dry season. However, the rainfall between June and November is only around 5 inches per month near the mouth of the Amazon, while further north in Macapa, on the equator, it can drop to under 2 inches per month, especially after September. In contrast, the rainfall during the rest of the year can reach up to 17 inches per month.
Recife, Bahia, and Northeast Brazil
This region of Brazil has a tropical monsoon climate, with strong wet and dry seasons. It is extremely hot, with high temperatures consistently in the high 80s and low temperatures in the low 70s. The coolest time of year is July and August, because the seasons are reversed south of the equator. Even then, the average high temperature is still over 80 degrees, although this is somewhat moderated by ocean breezes.
The rainy season runs from March to August. The heaviest rainfall usually comes during June and July, with an average of over 15 inches per month. However, a slight variation in the trade winds can make most of the rain miss the region entirely. In those seasons, drought and brush fires can be a serious issue. Even during the regular rainy season, rainfall drops off fast further inland.
Brasilia and the Brazilian highlands
Most of the Planalto Brasileiro is tropical savannah, which has a dry season and a humid season. This close to the equator, temperatures are fairly consistent year-round, with average high temperatures in the high 70s and low 80s, while average low temperatures range from the mid-50s up to the low 60s.
The coolest night temperatures fall between May and September, just before the humid season hits in October. The rainiest months are November through February, with an average rainfall that can reach 10 inches per month. However, it may not rain at all between May and August.
Rio de Janeiro, Sao Paulo, Santa Catarina, and Southeast Brazil
The few miles difference between Rio de Janeiro and Sao Paulo makes the difference between a tropical savannah climate and a humid subtropical climate. Proximity to ocean breezes and elevation makes a great deal of difference in both temperature and humidity levels. Persistent strong ocean winds can make even Sao Paulo feel cold.
On average, high temperatures in Rio de Janeiro range from the high 70s to low 80s, with the coolest months being May through October. Temperatures at night are roughly 10 degrees lower than their daytime highs.
Sao Paulo has roughly the same summer temperatures, but gets slightly colder during the winter, with June and July average highs only reaching the low 70s and nighttime temperatures dipping down into the mid-50s. However, sometimes Sao Paulo experiences a “little summer” at the end of July, with a few unseasonable days of temperatures in the low 80s. These kinds of sudden changes have given Sao Paulo a reputation for unreliable weather.
Rio de Janeiro has fairly consistent rainfall year-round, with a small spike in April and again in December. In these months, the monthly rainfall may hit 6 inches. Otherwise, the average monthly rainfall is 4 inches or less.
In contrast, Sao Paulo has a strong rainy season from October to March, with monthly rainfalls of nearly 10 inches during January and February. During July and August, Sao Paulo hardly gets any rain at all.
On Santa Catarina island, summer high temperatures are in the mid-80s and summer lows are in the low 70s. In winter, high temperatures average in the high 60s, while lows can dip into the mid-50s. There is a small rise in total rainfall during summer and a small dip in total rainfall during winter, but typical monthly precipitation only ranges from about 4 to 8 inches, with the rainiest months being February and March.
Severe storms used to be extremely uncommon in the northern parts of this region, although Sao Paulo does have the occasional severe thunderstorm. However, in January 2011, Rio de Janeiro experienced its first recorded tornado-like storm.
Iguacu Falls and South Brazil
The climate of the Iguacu Falls is highland subtropical, with hot summers and cool winters. Average summer high temperatures between November and March are in the low 90s, with lows in the high 60s. June through August are the coldest months, with daily highs in the low to mid 70s and night time lows below 50 degrees.
The driest months are July and August. There is also a rainfall spike in October, although most months can expect 4 or 5 inches of rain.
Further south in the Brazilian pampas, the temperatures get cooler, fog is much more common along the coastal region, and the changes of season are more sudden. With no mountains or other highlands to block wind and storms, the interior is often extremely windy after a frontal system has passed. The best time of year to visit this region is between September and February, before the heavy autumn rains hit.