Do you need to know, when is the best time to go to Jan Mayen? Then you should take a look here, what weather you can expect there during the year.
The climate of Jan Mayen is arctic maritime, you can expect quite frequent storms and almost persistent fog. Seasonal variations of temperature are relatively small, thanks to the influence of the Gulf Stream.
When speaking about the usual weather in this state, the information is relevant for example for these popular places: Jan Mayen.
Let's look now what weather you can expect in the area around the capital and in many other cities. The warmest month here is July, the average maximum temperature is 11.6 ℃ (52.88 ℉). The average minimum temperature in this month is 0.3 ℃ (32.54 ℉). The coldest month here is March, the average maximum temperature is 3.2 ℃ (37.76 ℉). The average minimum temperature in this month is -17.2 ℃ (1.04 ℉). 
When travelling to some places in Jan Mayen, always consider the altitude of the the place as well. The highest point here is Haakon VII Toppen on Beerenberg (2277 m) and the lowest point is Norwegian Sea (0 m). So there are quite big differences in altitudes in this country, so you can expect the weather to be different in different altitudes as well. Keep in mind, that the temperature usually decreases by 1.2 - 1.9 ℃ (2.2 - 3.5 ℉) per 200 m (656 ft), depending on the other conditions. (And we should add, that in the very special condition named thermal inversion even the temperature may be higher in higher altitudes.)
Typical (usual) weather in Jan Mayen in January is this: The average highest temperature in Jan Mayen in January is 4 ℃ (39.2 ℉). The average lowest temperature is -17 ℃ (1.4 ℉). At the beginning of January you can expect higher temperatures, the average highest temperature is around 4.15 ℃ (39.47 ℉). At the end of January you can expect lower temperatures, the average highest temperature is around 3.9 ℃ (39.02 ℉). The average rainfall is 61.1 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately -9223372036854775808:-9223372036854775808 (hours and minutes), in the middle of the month -9223372036854775808:-9223372036854775808 and at the end of the month 3:55.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in February is this: The average highest temperature in Jan Mayen in February is 3.8 ℃ (38.84 ℉). The average lowest temperature is -17.4 ℃ (0.68 ℉). At the beginning of February you can expect higher temperatures, the average highest temperature is around 3.9 ℃ (39.02 ℉). At the end of February you can expect lower temperatures, the average highest temperature is around 3.5 ℃ (38.3 ℉). The average rainfall is 53.5 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 3:55 (hours and minutes), in the middle of the month 6:53 and at the end of the month 9:22.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in March is this: The average highest temperature in Jan Mayen in March is 3.2 ℃ (37.76 ℉). The average lowest temperature is -17.2 ℃ (1.04 ℉). At the beginning of March you can expect higher temperatures, the average highest temperature is around 3.5 ℃ (38.3 ℉). At the end of March you can expect higher temperatures, the average highest temperature is around 4.15 ℃ (39.47 ℉). The average rainfall is 55.7 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 9:22 (hours and minutes), in the middle of the month 11:41 and at the end of the month 13:59.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.
Typical (usual) weather in Jan Mayen in April is this: The average highest temperature in Jan Mayen in April is 5.1 ℃ (41.18 ℉). The average lowest temperature is -10.6 ℃ (12.92 ℉). At the beginning of April you can expect lower temperatures, the average highest temperature is around 4.15 ℃ (39.47 ℉). At the end of April you can expect higher temperatures, the average highest temperature is around 5.85 ℃ (42.53 ℉). The average rainfall is 39.8 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 13:59 (hours and minutes), in the middle of the month 16:25 and at the end of the month 19:14.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in May is this: The average highest temperature in Jan Mayen in May is 6.6 ℃ (43.88 ℉). The average lowest temperature is -3.8 ℃ (25.16 ℉). At the beginning of May you can expect lower temperatures, the average highest temperature is around 5.85 ℃ (42.53 ℉). At the end of May you can expect higher temperatures, the average highest temperature is around 8.35 ℃ (47.03 ℉). The average rainfall is 40.9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 19:14 (hours and minutes), in the middle of the month -9223372036854775808:-9223372036854775808 and at the end of the month -9223372036854775808:-9223372036854775808.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in June is this: The average highest temperature in Jan Mayen in June is 10.1 ℃ (50.18 ℉). The average lowest temperature is -1.9 ℃ (28.58 ℉). At the beginning of June you can expect lower temperatures, the average highest temperature is around 8.35 ℃ (47.03 ℉). At the end of June you can expect higher temperatures, the average highest temperature is around 10.85 ℃ (51.53 ℉). The average rainfall is 35.5 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately -9223372036854775808:-9223372036854775808 (hours and minutes), in the middle of the month -9223372036854775808:-9223372036854775808 and at the end of the month -9223372036854775808:-9223372036854775808.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in July is this: The average highest temperature in Jan Mayen in July is 11.6 ℃ (52.88 ℉). The average lowest temperature is 0.3 ℃ (32.54 ℉). At the beginning of July you can expect lower temperatures, the average highest temperature is around 10.85 ℃ (51.53 ℉). At the end of July you can expect lower temperatures, the average highest temperature is around 11.6 ℃ (52.88 ℉). The average rainfall is 46.6 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately -9223372036854775808:-9223372036854775808 (hours and minutes), in the middle of the month -9223372036854775808:-9223372036854775808 and at the end of the month -9223372036854775808:-9223372036854775808.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in August is this: The average highest temperature in Jan Mayen in August is 11.6 ℃ (52.88 ℉). The average lowest temperature is 1.1 ℃ (33.98 ℉). At the beginning of August you can expect lower temperatures, the average highest temperature is around 11.6 ℃ (52.88 ℉). At the end of August you can expect lower temperatures, the average highest temperature is around 10.35 ℃ (50.63 ℉). The average rainfall is 59.7 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately -9223372036854775808:-9223372036854775808 (hours and minutes), in the middle of the month 19:05 and at the end of the month 16:20.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in September is this: The average highest temperature in Jan Mayen in September is 9.1 ℃ (48.38 ℉). The average lowest temperature is -2.3 ℃ (27.86 ℉). At the beginning of September you can expect higher temperatures, the average highest temperature is around 10.35 ℃ (50.63 ℉). At the end of September you can expect lower temperatures, the average highest temperature is around 8.45 ℃ (47.21 ℉). The average rainfall is 82 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 16:20 (hours and minutes), in the middle of the month 13:57 and at the end of the month 11:41.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in October is this: The average highest temperature in Jan Mayen in October is 7.8 ℃ (46.04 ℉). The average lowest temperature is -7.3 ℃ (18.86 ℉). At the beginning of October you can expect higher temperatures, the average highest temperature is around 8.45 ℃ (47.21 ℉). At the end of October you can expect lower temperatures, the average highest temperature is around 6.65 ℃ (43.97 ℉). The average rainfall is 80.7 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:41 (hours and minutes), in the middle of the month 9:23 and at the end of the month 6:57.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in November is this: The average highest temperature in Jan Mayen in November is 5.5 ℃ (41.9 ℉). The average lowest temperature is -11.4 ℃ (11.48 ℉). At the beginning of November you can expect higher temperatures, the average highest temperature is around 6.65 ℃ (43.97 ℉). At the end of November you can expect lower temperatures, the average highest temperature is around 4.9 ℃ (40.82 ℉). The average rainfall is 66.4 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 6:57 (hours and minutes), in the middle of the month 4:01 and at the end of the month -9223372036854775808:-9223372036854775808.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Jan Mayen in December is this: The average highest temperature in Jan Mayen in December is 4.3 ℃ (39.74 ℉). The average lowest temperature is -15.4 ℃ (4.28 ℉). At the beginning of December you can expect higher temperatures, the average highest temperature is around 4.9 ℃ (40.82 ℉). At the end of December you can expect lower temperatures, the average highest temperature is around 4.15 ℃ (39.47 ℉). The average rainfall is 64.9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately -9223372036854775808:-9223372036854775808 (hours and minutes), in the middle of the month -9223372036854775808:-9223372036854775808 and at the end of the month -9223372036854775808:-9223372036854775808.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.