Start of the seasons

The seasons begin at the equinoxes and solstices, four exact moments each year. In 2026, autumn starts in Brazil on March 20, 2026, winter on June 21, 2026, spring on September 22, 2026 and summer on December 21, 2026. All times below are in Brasília time (UTC-3) and in UTC, and the northern hemisphere has the opposite seasons.

Season dates for 2026

Season dates for 2027

Length of each season in 2026

The seasons are not equally long because the Earth's orbit is an ellipse: the planet moves faster when it is closer to the Sun (in January) and slower when it is farther away (in July). That is why winter in Brazil is the longest season and summer the shortest, while the northern hemisphere sees the opposite.

Seasons in each hemisphere

The seasons are opposite on either side of the equator. In Brazil and the rest of the southern hemisphere, autumn begins at the March equinox, winter at the June solstice, spring at the September equinox and summer at the December solstice. In the northern hemisphere the same four moments start spring, summer, autumn and winter. So when it is Christmas in Brazil, in the middle of summer, it is the start of winter in Europe and the United States.

Equinoxes and solstices explained

The Earth's axis is tilted about 23.4 degrees from the plane of its orbit, and this tilt, not the distance from the Sun, is what causes the seasons. At a solstice one hemisphere is leaning as far as possible toward the Sun: it gets the longest day of the year, while the other hemisphere has its shortest day. At an equinox the axis points sideways relative to the Sun, the Sun is directly above the equator, and day and night last almost exactly 12 hours everywhere on the planet. In fact the Earth is closest to the Sun in early January, which is summer in Brazil and winter in the north.

Why the dates vary between the 20th and the 23rd

A tropical year, the time to complete one cycle of seasons, lasts about 365.2422 days, while the calendar uses 365 or 366. Each common year the events slip about six hours later, and leap years pull them back. The Gregorian rule that skips leap years in century years not divisible by 400 adds a slower correction. The result is that the equinoxes and solstices wander between the 20th and the 23rd of their months. The dates also depend on the time zone: an event shortly after midnight UTC can fall on the previous evening in Brasília.

Brazil's climate does not follow the astronomical seasons

Most of Brazil lies within the tropics, where the contrast between seasons is mild and the main climate divide is between the wet and dry seasons. In the Southeast and Center-West the rainy season runs roughly from October to March, which coincides with astronomical spring and summer, and the dry season from April to September. In the Amazon the heaviest rain is from December to May, while the eastern coast of the Northeast gets most of its rain from April to July. Only the South, and the highlands of the Southeast, have four well-marked seasons, with frost in winter and occasional snow in the mountains. Meteorologists often use a simpler rule, grouping whole months: December to February for summer, March to May for autumn, June to August for winter and September to November for spring.

Season dates for other years

See also the Moon phase calendar, the sunrise and sunset times and the week number of the year.