The archipelago of the Bahamas is stretched along a northwest-southeast axis: the northernmost islands are located to the east of Florida, while the southernmost ones are located to the northwest of Haiti. The climate is subtropical in the north, and fully tropical in the south, with a hotter and rainy season from late April to early November. The trade winds temper the heat in the summer months.
Proceeding from north-west to south-east, there's an increase in the winter temperatures and a decrease in the summer precipitation: this means that the north-western islands (Grand Bahama, Little Abaco, Andros and New Providence, where the capital Nassau is located) are cooler in winter and rainier in summer.
In fact, in Freeport, in the north-west, rainfall amounts to almost 1,500 millimetres (60 inches) per year, while it drops to 1,200 mm (47 in) in Nassau, 1,100 mm (43 in) in Eleuthera and San Salvador, 800 mm (31.5 in) in Mayaguana, and just 650 mm (25.5 in) in Great Inagua. In the south-eastern islands, not only the total amount of rainfall is quite scarce, but also there is a fairly significant decrease in the rains in July.
Here is the average precipitation in Nassau, located, as mentioned, in the northwestern island of New Providence.
Average precipitation - Nassau

Nassau	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Nassau	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	35	45	45	80	115	160	150	135	165	165	85	40	1220
Prec.(in)	1.4	1.8	1.8	3.1	4.5	6.3	5.9	5.3	6.5	6.5	3.3	1.6	48
Days	6	6	5	6	11	14	16	16	17	15	9	9	130

And here is the average precipitation in Matthew Town, in the arid southern island of Great Inagua.
Average precipitation - Matthew Town

Matthew Town	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Matthew Town	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	50	35	35	40	85	30	20	50	85	120	70	35	660
Prec.(in)	2	1.4	1.4	1.6	3.3	1.2	0.8	2	3.3	4.7	2.8	1.4	26
Days	6	5	4	5	6	4	4	5	7	10	8	6	70

As for the temperatures, the main differences occur in winter, which is cooler in the northwest and warmer in the southeast, while the summer is hot and muggy everywhere.
Here are the average temperatures of Freeport, located in the island of Grand Bahama, the most northwestern of the archipelago, where temperatures resemble those of Miami, which is not far away.
Average temperatures - Freeport

Freeport	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Freeport	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	16	16	18	19	21	23	24	24	23	21	19	17
Max (°C)	24	24	26	27	30	31	32	32	32	30	27	25
Min (°F)	61	61	64	66	70	73	75	75	73	70	66	63
Max (°F)	75	75	79	81	86	88	90	90	90	86	81	77

In the coolest months (January and February), the average daily temperature is around 20 °C (68 °F) in the northernmost islands (Grand Bahama, Abaco), around 21 °C (70 °F) in New Providence and Eleuthera, 22.5 °C (72.5 °F) in San Salvador, 23 °C (73.5 °F) in Mayaguana, and 24.5 °C (76 °F) in Great Inagua. During winter, from December to March, cold air masses from the United States can lower the temperature for a few days, especially in the north-western islands, so that at night it can even get cold, below 10 °C in (50 °F) Freeport and Nassau; in addition, weather fronts can bring clouds and wind.
Here are the average temperatures in Nassau.
Average temperatures - Nassau

Nassau	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Nassau	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	17	17	18	19	21	23	24	24	24	22	21	18
Max (°C)	26	26	27	28	30	31	32	32	32	30	28	26
Min (°F)	63	63	64	66	70	73	75	75	75	72	70	64
Max (°F)	79	79	81	82	86	88	90	90	90	86	82	79

The temperatures in the warmest months (July and August) vary less from north to south, in fact they range from 27/28 °C (81/82 °F) in the northernmost islands, to 28/29 °C (82/84 °F) in the southern ones.
Here are the average temperatures of Abrahams Bay, in the southern island of Mayaguana.
Average temperatures - Abrahams Bay

Abrahams Bay	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Abrahams Bay	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	20	21	21	22	23	24	25	25	24	24	22	21
Max (°C)	26	27	27	28	30	31	31	32	31	31	28	27
Min (°F)	68	70	70	72	73	75	77	77	75	75	72	70
Max (°F)	79	81	81	82	86	88	88	90	88	88	82	81

The amount of sunshine in the Bahamas is good throughout the year, because the summer rains fall mainly in the form of showers and thunderstorms, in late afternoon or evening, so the sky doesn't remain overcast for a long time. Here, for example, the average hours of sunshine per day in Nassau.
Sunshine - Nassau

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

From June to November, however, the Bahamas can be affected by hurricanes, tropical cyclones of the Atlantic and the Caribbean, which are more likely from August to October.



The sea is warm enough for swimming all year round, even though it's slightly cooler in the northern islands, at least in the winter months: at Nassau the water temperature ranges from 24 °C (75 °F) in February and March, to 29 °C (84 °F) from July to September, while in the southern islands it does not drop below 26 °C (79 °F) even in winter.
Sea temperature - Nassau

Nassau	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Nassau	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	25	24	24	25	26	28	29	29	29	28	27	26
Sea (°F)	77	75	75	77	79	82	84	84	84	82	81	79

In general, the best time to visit the Bahamas is the dry season, from late November to mid-April. However, in the north-western islands, from December to March the temperature is often not high enough for a beach holiday, and sometimes there are also some cool and windy days. In the southernmost islands, however, and in particular in Inagua and Great Inagua, winter is warm enough to enjoy the sun and the sea, while in the northernmost islands you may prefer April (the best) and May (still good but with the first summer rains).
In the rainy season, the heat is sweltering, and thunderstorms can be intense, even though the sun is still frequent. If you want to choose the summer, the month of July will be preferable, because there's a relative break in the rains (though not in Nassau and in the westernmost islands), and because hurricanes are less likely than in August.


From November to April, in the northernmost islands: light clothing, but also a sweatshirt or sweater, a scarf for the breeze, jacket and umbrella; in the southern islands: light clothes, a sweatshirt for the evening, a scarf for the breeze.
From May to October: light tropical clothing, possibly a light sweatshirt and a light raincoat for thunderstorms.
For the reef, equipment for snorkeling, water shoes or rubber soled shoes.