Singapore weather is based on a tropical climate and with the Equator just 1.5 degrees south, days are generally sunny and seasons less distinct. Although rainfall is experienced almost daily, showers are sudden and heavy but short lived. Nevertheless, the majority of Singapore's rainfall occurs from November to January during the northeast monsoon. During this time, Singapore's weather can sometimes be characterised by longer spells of continuous rain however temperatures still remain warm.
Visitors are recommended to carry umbrellas as they not only provide protection from the sun, but also from the impressive thunderstorms that can occur at any time of the day throughout the year. Sumatran forest fires from May to October can also cause an unpredictable and dense haze that settles on the city but dissipates quite quickly.
Singapore weather is always warm, with temperatures averaging around 32°C during the day and 25°C at night from December to January while the rest of the year averages around 33°C during the day and 26°C at night. As you may be able to tell, there is little distinction between 'seasons' with such little variation in temperature. In fact, the higher temperatures and humidity even at night combined with little to no wind means that Singapore weather can be a little uncomfortable to those unaccustomed to such conditions, especially to visitors from colder climates. Limiting the time spent outdoors as well as your level of exertion will help to preserve energy.
The locals themselves dislike the heat so you'll find that everywhere you go is air conditioned. This provides a welcome relief from the heat. Aside from any time you spend outdoors, you should be able to enjoy your time in Singapore in the comfort of air conditioning thanks to air conditioned accommodation, shopping malls and public transport.