Kiribati is tropical year-round, hot and humid with temperatures hovering between 26–32°C. The meaningful distinction is between the drier trade-wind season and the wetter months.
May to October is the most comfortable time to visit. The southeast trade winds moderate the heat, humidity drops a little, seas are calmer, and visibility underwater is at its best. This is peak season for fishing and diving on Kiritimati, and the better time to sail or take inter-island vessels.
November to April is hotter and wetter. Rain tends to come in short, sharp bursts rather than all-day downpours, so it rarely ruins a whole day. This is also cyclone season — storm surges can be sudden and serious on low-lying atolls. That said, this period sees fewer tourists and lower accommodation prices where such things apply.
Independence Day falls on July 12, and the surrounding week sees canoe races, traditional dancing, and sporting competitions centred on South Tarawa. It is the most lively cultural moment of the year and worth timing a visit around if you can.
The Gilbert Islands and Phoenix Islands share broadly similar climates. The Line Islands (including Kiritimati) lie further east and can have distinct weather patterns — the north of Kiritimati is drier than the south.