Map from Google - Maldives

The Maldives have a tropical climate, hot all year round and influenced by monsoons: the south-west monsoon, from late April to October, it's stronger in the northern islands, and it's accompanied by the wind, which can make the sea rough and therefore may discourage activities such as diving, and is also accompanied by increased humidity and more frequent cloudiness. The northeast monsoon, from October to December, it's quieter and simply brings showers and thunderstorms in the afternoon or evening, especially in southern atolls.
The driest period, outside the monsoons, runs from January to April.

The temperatures are stable: highs are around 30 °C (86 °F) and lows around 25 °C (77 °F) for most of the year. Even the relative humidity is high and stable throughout the year, around 80%. However, between February and May, there is a slight increase in temperature, therefore the feeling of sultriness, especially in the northern atolls, given that in this period the maximum rises to 31/32 °C (88/90 °F), and the minimum to 26/27 °C (79/81 °F).
Here are the average temperatures of the capital Malé.
Average temperatures - Malé
MaléJanFebMarAprMayJunJulAugSepOctNovDec
MaléJFMAMJJASOND
Min (°C)252526262626252525252525
Max (°C)303131323130303030303030
Min (°F)777779797979777777777777
Max (°F)868888908886868686868686

The rains occur, as it's common in tropical climate areas, mostly in the form of short and intense downpour or thunderstorm. They are a bit more abundant in the southern atolls, where they hover around 2,200/2,300 millimetres (87/91 inches) per year, and less in the north, where they hover around 1,700/1,800 mm (67/71 in) per year. The difference is mainly due to the fact that in the central and northern atolls there is a relatively dry season from January to mid-April, which is more pronounced in the northernmost atolls.
In the capital, Malé, situated at the centre, they are about 1,950 mm (77 in) per year. Here there is a rainy period which runs from May to December, while the least rainy months are January, February and March, when precipitation drops below 100 mm (4 in) per month.
Here is the average precipitation in Malé.
Average precipitation - Malé
MaléJanFebMarAprMayJunJulAugSepOctNovDecYear
MaléJFMAMJJASONDY
Prec. (mm)9070801302101851601852152301902001945
Prec.(in)3.52.83.15.18.37.36.37.38.59.17.57.976.6
Days558101614131415161313142

Here is the average precipitation in Gan, on Addu Atoll (or Seenu), the southernmost island of the Maldives. Here there is no dry season, so the climate can be defined equatorial (in fact, the atoll is located just south of the equator).
Average precipitation - Gan
GanJanFebMarAprMayJunJulAugSepOctNovDecYear
GanJFMAMJJASONDY
Prec. (mm)2001351451702251851751902152752002502365
Prec.(in)7.95.35.76.78.97.36.97.58.510.87.99.893.1
Days101013141612141515181516168

The amount of sunshine in the Maldives is good from January to April, and the sunniest months are February and March; in the rest of the year it is acceptable, because even in the rainiest months the sun shines on average for a few hours (about 7) a day, although there may be days or periods of a few days when the sky is often cloudy, especially in the season of the south west monsoon (late April-October).

The Maldives can be occasionally reached by tropical cyclones, which usually move at higher latitudes, in the northern Indian Ocean. The cyclones are formed more often between April and December, but due to the warm sea, they may occur throughout the year. Anyway the southern atolls (Huvadhu, Addu, Fuvahmulah) are protected from them, since they are located near the Equator, where cyclones cannot form nor survive.

Maldives

The sea is warm all year round, since the water temperature varies from 28 °C to 30 °C (82 to 86 °F).
Sea temperature - Malé
MaléJanFebMarAprMayJunJulAugSepOctNovDec
MaléJFMAMJJASOND
Sea (°C)282829303029292929282928
Sea (°F)828284868684848484828482

When to go

The best time to visit the Maldives runs from January to mid-April, since it is the driest and sunniest of the year. Even in this period, however, there can be showers and thunderstorms in the afternoon, especially in the southern islands.
If you want to travel in the summer, you can choose the southern islands, which are less exposed to the south-west monsoon and are therefore less windy and more sunny, and are also protected from tropical cyclones.

What to pack

All year round: lightweight, tropics-friendly clothing, light sweatshirt for the evening, scarf for the breeze, light raincoat or umbrella, sunglasses, sunscreen.
For the reef, equipment for snorkeling, water shoes or rubber soled shoes.