Due to its high proximity to the equator, Bogota and the rest of Colombia don't have seasons. Bogota is a high-altitude city with a slightly cold weather, although it has many fluctuations along the whole year, with two main rainy seasons: the first between March and May, and the second one between September and November. For this reason, many locals are used to wearing warm clothing daily, specially because the nights are usually cold all throughout the year.
In order to dress properly in a city with a predominantly chill weather, but also very unpredictable, the coats, sweaters, jackets and scarves are of everyday use. Besides, during the rainy seasons, it is necessary to carry an umbrella, because rainfalls are very common, and in some CASES, they can turn into hailstorms. The temperature can drops even to 2°C (35,6°F) in these seasons, especially at night.
However, it is no secret that the city has funny changes and there are sunny days in mid year (from May to the beginning of September) and from the end of the year to the first months of the next (December, January and February). During these seasons, people don't wear short pants or sandals; instead, they use a more informal clothing, like sportive shoewear, shirts, short-sleeved shirts and jeans. In any case, it is important to keep in mind that the city's weather is quite unpredictable, so it is always good to be well prepared and carry a bag with clothes to keep yourself warm.