The archipelago of Bermuda has a very mild climate, due to the influence of the Gulf Stream, but it is not a tropical paradise, at least in winter.
The annual precipitation is around 1,400 millimetres (55 inches); the rains are fairly evenly distributed over the seasons, because the flow of weather fronts in winter is replaced by the tropical rains in the summer months. Anyway, the least rainy months are April and May, while the rainiest month is October.
Here is the average precipitation in Hamilton, the capital.
Average precipitation - Hamilton

Hamilton	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Hamilton	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	130	115	110	90	85	130	115	130	130	160	105	115	1410
Prec.(in)	5.1	4.5	4.3	3.5	3.3	5.1	4.5	5.1	5.1	6.3	4.1	4.5	55.5
Days	13	12	11	8	7	11	10	12	12	13	11	13	133

In winter, from November to March, temperatures are very mild, with lows around 15/17 °C (59/63 °F) and highs around 20/22 °C (68/72 °F). Sometimes the weather is nice and the sun shines, but this kind of weather is not always guaranteed: in fact there is no shortage of rainfall, so much so that there are about 11/13 rainy days per month, and there can be windy days as well.
Summer in Bermuda is hot and muggy, with highs around 30 °C (86 °F) in July and August, although the heat is tempered by the breeze. There are about 10/12 days of rain per month, but usually in this season the rain comes in the form of short and intense showers and thunderstorms, which break out in the evening and do not affect much the sunshine amount.
Here are the average temperatures.
Average temperatures - Hamilton

Hamilton	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Hamilton	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	16	16	16	17	20	23	24	25	24	21	19	17
Max (°C)	20	20	20	22	24	27	29	30	29	26	24	21
Min (°F)	61	61	61	63	68	73	75	77	75	70	66	63
Max (°F)	68	68	68	72	75	81	84	86	84	79	75	70

The hours of sunshine in Bermuda are not many from November to March, when there are several cloudy days, while from April to September, the percentage of sunshine is good.
Sunshine - Hamilton

Hamilton	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Hamilton	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	5	5	6	8	8	9	9	9	7	6	6	5

The sea is cool in winter, when the water temperature is around 19/20 °C (66/68 °F); the sea becomes pleasantly warm from June to October, with a maximum in August, when the temperature reaches 28 °C (82 °F).
Sea temperature - Bermuda

Bermuda	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Bermuda	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	20	20	19	20	21	24	27	28	27	25	23	22
Sea (°F)	68	68	66	68	70	75	81	82	81	77	73	72

Hurricanes

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Sometimes the archipelago can be hit by hurricanes. The hurricane season runs from June to November, although they are more likely from August to October. In general, hurricanes do not hit Bermuda at the peak of their violence, because the ocean at this latitude is less warm than the Gulf of Mexico, however, they can still bring strong winds and heavy rains.
Some hurricanes that hit Bermuda with considerable intensity were the "Hurricane of Havana and Bermuda" in October 1926, Hurricane Emily in September 1987, Fabian in August 2003, Arlene in August 1963, Fay and Gonzalo, both in October 2014, and Nicole in October 2016.

When to go

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Having a favorable climate, Bermuda can be visited all year round, in winter to relax, play sports or explore nature, in summer for swimming and sunbathing.
In summer, however, there's some risk of hurricanes.
All in all, April and May seem to be the best months, especially May, at least with regard to weather conditions, since it's still a bit cool for swimming: the daytime temperature is around 24 °C (75 °F), while the sea temperature is around 21 °C (70 °F).

What to pack

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From December to April: light clothes, but also sweatshirt or sweater, jacket and umbrella.
From June to September: summer clothing, a light sweatshirt and a light raincoat for thunderstorms.