Do you need to know, when is the best time to go to Guernsey? Then you should take a look here, what weather you can expect there during the year.
The climate of Guernsey is temperate. You can expect mild winters and cool summers, but about half of days are overcast. Snow falls only rarely and almost never accumulates. The weather can be quite cold here, but temperatures rarely drop below freezing.
When speaking about the usual weather in this state, the information is relevant for example for these popular places: Alderney, Herm, Saint Martin, Saint Peter Port, Sark.
Let's look now what weather you can expect here. The warmest month here is August, the average maximum temperature is 20.1 ℃ (68.18 ℉). The average minimum temperature in this month is 14 ℃ (57.2 ℉). The coldest month here is February, the average maximum temperature is 8.4 ℃ (47.12 ℉). The average minimum temperature in this month is 4.6 ℃ (40.28 ℉). The most rainy month here is December, the average number of rainy days is 18.8. The least rainy month here is July, the average number of rainy days is 9.5. 
Typical (usual) weather in Guernsey in January is this: The average highest temperature in Guernsey in January is 8.5 ℃ (47.3 ℉). The average lowest temperature is 5 ℃ (41 ℉). At the beginning of January you can expect higher temperatures, the average highest temperature is around 9.15 ℃ (48.47 ℉). At the end of January you can expect lower temperatures, the average highest temperature is around 8.45 ℃ (47.21 ℉). The average number of rainy days in January is 18.7. The average rainfall is 90.1 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 8:13 (hours and minutes), in the middle of the month 8:37 and at the end of the month 9:17.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in February is this: The average highest temperature in Guernsey in February is 8.4 ℃ (47.12 ℉). The average lowest temperature is 4.6 ℃ (40.28 ℉). At the beginning of February you can expect higher temperatures, the average highest temperature is around 8.45 ℃ (47.21 ℉). At the end of February you can expect higher temperatures, the average highest temperature is around 9.05 ℃ (48.29 ℉). The average number of rainy days in February is 15.7. The average rainfall is 75.7 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 9:17 (hours and minutes), in the middle of the month 10:06 and at the end of the month 10:59.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in March is this: The average highest temperature in Guernsey in March is 9.7 ℃ (49.46 ℉). The average lowest temperature is 5.5 ℃ (41.9 ℉). At the beginning of March you can expect lower temperatures, the average highest temperature is around 9.05 ℃ (48.29 ℉). At the end of March you can expect higher temperatures, the average highest temperature is around 10.6 ℃ (51.08 ℉). The average number of rainy days in March is 15.8. The average rainfall is 65.1 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 10:59 (hours and minutes), in the middle of the month 11:54 and at the end of the month 12:50.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in April is this: The average highest temperature in Guernsey in April is 11.5 ℃ (52.7 ℉). The average lowest temperature is 6.3 ℃ (43.34 ℉). At the beginning of April you can expect lower temperatures, the average highest temperature is around 10.6 ℃ (51.08 ℉). At the end of April you can expect higher temperatures, the average highest temperature is around 13.1 ℃ (55.58 ℉). The average number of rainy days in April is 13.4. The average rainfall is 51.6 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 12:50 (hours and minutes), in the middle of the month 13:44 and at the end of the month 14:35.These numbers above are valid primarily for the capital and the area around it.
Typical (usual) weather in Guernsey in May is this: The average highest temperature in Guernsey in May is 14.7 ℃ (58.46 ℉). The average lowest temperature is 9 ℃ (48.2 ℉). At the beginning of May you can expect lower temperatures, the average highest temperature is around 13.1 ℃ (55.58 ℉). At the end of May you can expect higher temperatures, the average highest temperature is around 15.95 ℃ (60.71 ℉). The average number of rainy days in May is 12.5. The average rainfall is 48.9 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 14:35 (hours and minutes), in the middle of the month 15:20 and at the end of the month 15:55.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in June is this: The average highest temperature in Guernsey in June is 17.2 ℃ (62.96 ℉). The average lowest temperature is 11.2 ℃ (52.16 ℉). At the beginning of June you can expect lower temperatures, the average highest temperature is around 15.95 ℃ (60.71 ℉). At the end of June you can expect higher temperatures, the average highest temperature is around 18.45 ℃ (65.21 ℉). The average number of rainy days in June is 10.3. The average rainfall is 45 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 15:55 (hours and minutes), in the middle of the month 16:14 and at the end of the month 16:14.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in July is this: The average highest temperature in Guernsey in July is 19.7 ℃ (67.46 ℉). The average lowest temperature is 13.5 ℃ (56.3 ℉). At the beginning of July you can expect lower temperatures, the average highest temperature is around 18.45 ℃ (65.21 ℉). At the end of July you can expect higher temperatures, the average highest temperature is around 19.9 ℃ (67.82 ℉). The average number of rainy days in July is 9.5. The average rainfall is 37.3 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 16:14 (hours and minutes), in the middle of the month 15:54 and at the end of the month 15:18.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in August is this: The average highest temperature in Guernsey in August is 20.1 ℃ (68.18 ℉). The average lowest temperature is 14 ℃ (57.2 ℉). At the beginning of August you can expect lower temperatures, the average highest temperature is around 19.9 ℃ (67.82 ℉). At the end of August you can expect lower temperatures, the average highest temperature is around 18.9 ℃ (66.02 ℉). The average number of rainy days in August is 11.2. The average rainfall is 45.2 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 15:18 (hours and minutes), in the middle of the month 14:33 and at the end of the month 13:42.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in September is this: The average highest temperature in Guernsey in September is 17.7 ℃ (63.86 ℉). The average lowest temperature is 12.6 ℃ (54.68 ℉). At the beginning of September you can expect higher temperatures, the average highest temperature is around 18.9 ℃ (66.02 ℉). At the end of September you can expect lower temperatures, the average highest temperature is around 16.25 ℃ (61.25 ℉). The average number of rainy days in September is 13.3. The average rainfall is 65.7 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 13:42 (hours and minutes), in the middle of the month 12:48 and at the end of the month 11:54.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in October is this: The average highest temperature in Guernsey in October is 14.8 ℃ (58.64 ℉). The average lowest temperature is 10.9 ℃ (51.62 ℉). At the beginning of October you can expect higher temperatures, the average highest temperature is around 16.25 ℃ (61.25 ℉). At the end of October you can expect lower temperatures, the average highest temperature is around 13.35 ℃ (56.03 ℉). The average number of rainy days in October is 15.6. The average rainfall is 90.9 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 11:54 (hours and minutes), in the middle of the month 10:59 and at the end of the month 10:07.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in November is this: The average highest temperature in Guernsey in November is 11.9 ℃ (53.42 ℉). The average lowest temperature is 8 ℃ (46.4 ℉). At the beginning of November you can expect higher temperatures, the average highest temperature is around 13.35 ℃ (56.03 ℉). At the end of November you can expect lower temperatures, the average highest temperature is around 10.85 ℃ (51.53 ℉). The average number of rainy days in November is 18.6. The average rainfall is 95.5 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 10:07 (hours and minutes), in the middle of the month 9:18 and at the end of the month 8:39.These numbers above are valid primarily for the capital and the area around it.Typical (usual) weather in Guernsey in December is this: The average highest temperature in Guernsey in December is 9.8 ℃ (49.64 ℉). The average lowest temperature is 6.3 ℃ (43.34 ℉). At the beginning of December you can expect higher temperatures, the average highest temperature is around 10.85 ℃ (51.53 ℉). At the end of December you can expect lower temperatures, the average highest temperature is around 9.15 ℃ (48.47 ℉). The average number of rainy days in December is 18.8. The average rainfall is 107.1 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 8:39 (hours and minutes), in the middle of the month 8:14 and at the end of the month 8:09.These numbers above are valid primarily for the capital and the area around it.