The climate in St. Kitts and Nevis is tropical, hot and humid all year round, with a relatively cool and dry season from January to mid-April, and a hot, humid and rainy season from mid-June to mid-November. In the former period, the northeast trade winds, constant winds typical of tropical climates, blow steadily and with moderate intensity, while in the latter period the winds are more irregular, and may have some breaks, increasing the feeling of sultriness. Between them there are two transitional periods: from mid November to early January (when the northeast wind starts to blow, the temperature decreases a bit and the weather gets better), and from mid-April to Mid-June (when both the temperature and the frequency of downpours gradually increase).
Saint Kitts and Nevis is a state in the group of the Lesser Antilles, formed by the two islands of the same name, with Basseterre as the capital city.
The daily average temperature is around 25 degrees Celsius (77 °F) in January and February, and 28 °C (82 °F) from June to October, which is the hottest period.
Here are the average temperatures of Basseterre.
Average temperatures - Basseterre

Basseterre	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Basseterre	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	22	22	23	23	24	25	25	25	25	25	24	23
Max (°C)	28	28	29	29	30	31	31	31	31	31	30	29
Min (°F)	72	72	73	73	75	77	77	77	77	77	75	73
Max (°F)	82	82	84	84	86	88	88	88	88	88	86	84

Rainfall amounts to around 1,200 millimetres (47 inches) per year along the coast. The rainiest period, in which precipitation exceeds 100 mm (4 in) per month, runs from July to November, while the driest runs from February to April, when rainfall does not exceed 60 mm (2.4 in) per month.
Here is the average precipitation.
Average precipitation - Basseterre

Basseterre	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Basseterre	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	90	50	55	60	90	85	115	130	140	125	130	90	1160
Prec.(in)	3.5	2	2.2	2.4	3.5	3.3	4.5	5.1	5.5	4.9	5.1	3.5	45.7
Days	12	9	9	8	10	10	13	14	14	13	15	13	140

The rains, as is normally the case in countries having a tropical climate, occur primarily in the form of downpour or thunderstorm, so they do not reduce too much the hours of sunshine, and are quite irregular, which means that there may be periods without rainfall in every month of the year, but also periods of heavy rains for several consecutive days.
In fact, the amount of sunshine is good all year round, at least along the coasts, as can be seen in the following table.
Sunshine - Basseterre

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

In each of the two islands there is a volcano: Mount Liamuiga, formerly Mount Misery, 1,156 metres (3,793 feet) high, and Nevis Peak, 985 metres (3,232 feet) high; on the slopes the climate is very humid, with more abundant rainfall than on the coast, so that above 900 metres (3,000 feet), the vegetation becomes lush and cloud forests grow.

From June to November, as in the whole area of the Caribbean and the West Indies, there is the danger of tropical storms and hurricanes, with greater probability from August to October.



The sea in Saint Kitts and Nevis is warm enough for swimming all year round, as we can see from the following table.
Sea temperature - Basseterre

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

The best time to visit Saint Kitts and Nevis goes from December to April, being the least hot, and also outside the period of hurricanes; within this period, in particular, the period from February to April stands out as the driest. In the summer months, the weather is hot and sultry, and thunderstorms are more common, although they rarely lead to very heavy rains; however, in August and September there's a greater chance of heavy rains than in June and July, and also a greater chance of hurricanes.


From December to April: light clothing, a light sweatshirt for the evening.
From May to November: lightweight clothing, possibly a light sweatshirt and a light raincoat for thunderstorms.