Anguilla has a tropical climate, hot all year round, with a slightly cooler period from December to March, and a hotter and muggy period from May to October. Luckily, sea breezes relieve a bit the heat of the day.
Here are the average temperatures in the capital, The Valley.
Average temperatures - The Valley

The Valley	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
The Valley	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	23	23	23	25	25	26	26	26	26	26	25	24
Max (°C)	28	28	28	28	30	31	31	31	31	30	29	28
Min (°F)	73	73	73	77	77	79	79	79	79	79	77	75
Max (°F)	82	82	82	82	86	88	88	88	88	86	84	82

Anguilla is located in the northernmost part of the Lesser Antilles, and it's a British overseas territory, formed by the main island, where the capital is found, plus some small coral islands.
Rainfall is generally not very abundant, since it amounts to around 1,000 millimetres (40 inches) per year. February and March are usually the driest months, with about 45 mm (1.8 in) per month on average, while in the rest of the year the rains are quite irregular, although they rarely reach high values. Normally the rainy period goes from August to November, however, with moderate rainfall, between 100 and 130 mm (4 and 5 in) per month. During some years there may be another peak of precipitation in April and May. As normally happens in tropical areas, the rains usually fall in the form of downpour or thunderstorm, in days in which the sun shines for a few hours anyway. More rarely, there can be heavy and prolonged rains when tropical depressions and hurricanes hit the islands; this can happen, in Anguilla as in other Caribbean islands, from June to November (but especially from August to October).
Here is the average precipitation.
Average precipitation - The Valley

The Valley	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
The Valley	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	65	45	45	65	95	60	75	100	130	110	125	90	1005
Prec.(in)	2.6	1.8	1.8	2.6	3.7	2.4	3	3.9	5.1	4.3	4.9	3.5	39.6
Days	10	8	7	8	10	8	9	12	13	12	13	12	122

The amount of sunshine is good all year round, as can be seen in the following table.
Sunshine - The Valley

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

The sea in Anguilla is warm enough for swimming all year round, although of course it's a bit warmer in the summer months.
Sea temperature - The Valley

The Valley	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
The Valley	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	26	26	26	26	27	28	28	28	29	29	28	27
Sea (°F)	79	79	79	79	81	82	82	82	84	84	82	81

The best time to visit Anguilla runs from December to April, when the temperatures are a bit lower and we are outside of the hurricane season, and particularly in February and March, which are the driest months. In summer, June and July are usually a bit less rainy than August, and also have a lower probability of hurricanes.


From December to April: light clothing, a light sweater or sweatshirt for the evening and for the breeze.
From May to November: lightweight, loose fitting clothing, possibly a light sweatshirt and a light raincoat for thunderstorms.
For the reef, equipment for snorkeling, water shoes or rubber soled shoes.