In Mont Saint-Michel, a small island of Normandy and Unesco World Heritage Site, the climate is oceanic, cool and wet most of the year. The temperatures are similar to those of the coastal area of Normandy, as the island is located very near the coast, however, the presence of the sea creates a humid microclimate, a bit cooler during the day, especially in summer.
Here are the average temperatures.
Average temperatures - Mont St Michel

Mont St Michel	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Mont St Michel	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	3	4	5	6	8	10	12	13	11	9	5	4
Max (°C)	9	10	12	13	16	18	20	21	19	16	12	10
Min (°F)	37	39	41	43	46	50	54	55	52	48	41	39
Max (°F)	48	50	54	55	61	64	68	70	66	61	54	50

Precipitation is not particularly abundant, given that it amounts to 750 millimetres (30 inches) per year, but it's frequent and well distributed over the seasons, with a relative minimum in spring and summer, and a maximum in autumn and winter.
Here is the average precipitation.
Average precipitation - Mont St Michel

Mont St Michel	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Mont St Michel	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	70	50	60	50	50	55	55	55	70	80	90	70	755
Prec. (in)	2.8	2	2.4	2	2	2.2	2.2	2.2	2.8	3.1	3.5	2.8	29.7
Days	18	14	16	15	15	13	12	12	14	15	18	17	179

The wind blows frequently throughout the year, and can be strong, especially from November to March.

Winter, from December to February, is quite cold: the average temperature in January is 6 °C (43 °F), but the air is humid, it often rains and the wind blows. The temperature can be milder, reaching 12/14 °C (53/57 °F), when currents from the Atlantic Ocean prevail, while cold air masses from Russia can lower the temperature to a few degrees below freezing (0 °C or 32 °F). In these situations of cold weather, even snowfall can occur.

Spring, from March to May, is very cool, and even a bit cold in March, and then it becomes gradually milder with each passing week. However, there may be cold days still in April and early May. The rains are frequent, much like in the rest of the year, although in this season they are less abundant.

Summer, from June to August, is cool: the maximum temperatures reach 20/21 °C (68/70 °F) in July and August. There is a fair amount of cloudy and rainy days, with highs below 20 °C (68 °F), alternating with warmer and sunnier periods, in which the temperature can touch or exceed 25 °C (77 °F). Even in this season, it rains on average for about 12/13 days per month.

Autumn, from September to November, is initially a pleasant season, then gradually becomes more cold, cloudy and rainy.



The amount of sunshine in Mont Saint-Michel is scarce in late autumn and winter, when the sun is rarely seen, while from April to September it is all in all acceptable.
Sunshine - Mont St Michel

Mont St Michel	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Mont St Michel	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	2	3	4	5	6	7	7	6	6	4	3	2

The sea is not recommended for swimming, especially for those who suffer from the cold, being a bit cold even in summer, as it reaches 17 °C (63 °F) in July and September, and 18 °C (64 °F) August, as can be seen in the following table.
Sea temperature - Mont St Michel

Mont St Michel	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Mont St Michel	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	10	9	9	10	12	14	17	18	17	15	13	12
Sea (°F)	50	48	48	50	54	57	63	64	63	59	55	54

The best time to visit Mont Saint-Michel is summer, from June to August or mid-September. It's better to bring a sweatshirt, a light jacket and umbrella, especially in June and September. July and August are the warmest months, but it should be remembered that being the high season, especially in August, there are many visitors.
To visit Mont-Saint-Michel it is useful to check the tide timetables: the strongest (and therefore the most spectacular) tides, occur 36 to 48 hours after full moon and new moon, though it also depends on weather conditions. There are, however, specific timetables, showing the indicative forecast of the daily tides for the next months. When on the spot, you must pay attention to the rapid return of the tide, which can take by surprise those who may linger on the beach, where there is also quicksand.