Do you need to know, when is the best time to go to United Kingdom? Then you should take a look here, what weather you can expect there during the year.
The climate of United Kingdom is temperate, weather is moderated by prevailing southwest winds over the North Atlantic Current. More than one-half of the days are overcast. Weather is usually quite unstable here. Generally speaking, you can expect cool and often cloudy weather. You can also expect warmer weather in the southern part of UK.
As United Kingdom has a really huge area, the information below relate mostly only to the area around the capital of this country. To see information about other places, please, choose one of these areas: England, Northern Ireland, Scotland, Wales.
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 23.9 ℃ (75.02 ℉). The average minimum temperature in this month is 14 ℃ (57.2 ℉). The coldest month here is January, the average maximum temperature is 8.1 ℃ (46.58 ℉). The average minimum temperature in this month is 3.4 ℃ (38.12 ℉). The most rainy month here is January, the average number of rainy days is 11.2. The least rainy month here is July, the average number of rainy days is 6.3. 
When travelling to some places in United Kingdom, always consider the altitude of the the place as well. The highest point here is Ben Nevis (1343 m) and the lowest point is The Fens (-4 m). So the differences in altitudes in this country are not negligible and you should expect the weather to be different in places in different altitudes. 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 United Kingdom in January is this: The average highest temperature in United Kingdom in January is 8.1 ℃ (46.58 ℉). The average lowest temperature is 3.4 ℃ (38.12 ℉). At the beginning of January you can expect higher temperatures, the average highest temperature is around 8.3 ℃ (46.94 ℉). At the end of January you can expect higher temperatures, the average highest temperature is around 8.4 ℃ (47.12 ℉). The average number of rainy days in January is 11.2. The average rainfall is 42.1 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 7:54 (hours and minutes), in the middle of the month 8:20 and at the end of the month 9:04.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 United Kingdom in February is this: The average highest temperature in United Kingdom in February is 8.7 ℃ (47.66 ℉). The average lowest temperature is 3 ℃ (37.4 ℉). At the beginning of February you can expect lower temperatures, the average highest temperature is around 8.4 ℃ (47.12 ℉). At the end of February you can expect higher temperatures, the average highest temperature is around 10.1 ℃ (50.18 ℉). The average number of rainy days in February is 8.6. The average rainfall is 36.9 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 9:04 (hours and minutes), in the middle of the month 9:56 and at the end of the month 10:54.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 United Kingdom in March is this: The average highest temperature in United Kingdom in March is 11.5 ℃ (52.7 ℉). The average lowest temperature is 4.9 ℃ (40.82 ℉). At the beginning of March you can expect lower temperatures, the average highest temperature is around 10.1 ℃ (50.18 ℉). At the end of March you can expect higher temperatures, the average highest temperature is around 13.2 ℃ (55.76 ℉). The average number of rainy days in March is 9.9. The average rainfall is 40.7 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 10:54 (hours and minutes), in the middle of the month 11:53 and at the end of the month 12:53.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 United Kingdom in April is this: The average highest temperature in United Kingdom in April is 14.9 ℃ (58.82 ℉). The average lowest temperature is 6 ℃ (42.8 ℉). At the beginning of April you can expect lower temperatures, the average highest temperature is around 13.2 ℃ (55.76 ℉). At the end of April you can expect higher temperatures, the average highest temperature is around 16.7 ℃ (62.06 ℉). The average number of rainy days in April is 9.1. 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 12:53 (hours and minutes), in the middle of the month 13:51 and at the end of the month 14:47.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 United Kingdom in May is this: The average highest temperature in United Kingdom in May is 18.5 ℃ (65.3 ℉). The average lowest temperature is 9 ℃ (48.2 ℉). At the beginning of May you can expect lower temperatures, the average highest temperature is around 16.7 ℃ (62.06 ℉). At the end of May you can expect higher temperatures, the average highest temperature is around 19.95 ℃ (67.91 ℉). The average number of rainy days in May is 9.2. The average rainfall is 44.8 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 14:47 (hours and minutes), in the middle of the month 15:36 and at the end of the month 16:15.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 United Kingdom in June is this: The average highest temperature in United Kingdom in June is 21.4 ℃ (70.52 ℉). The average lowest temperature is 11.8 ℃ (53.24 ℉). At the beginning of June you can expect lower temperatures, the average highest temperature is around 19.95 ℃ (67.91 ℉). At the end of June you can expect higher temperatures, the average highest temperature is around 22.65 ℃ (72.77 ℉). The average number of rainy days in June is 7.3. The average rainfall is 48.6 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 16:15 (hours and minutes), in the middle of the month 16:36 and at the end of the month 16:35.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 United Kingdom in July is this: The average highest temperature in United Kingdom in July is 23.9 ℃ (75.02 ℉). The average lowest temperature is 14 ℃ (57.2 ℉). At the beginning of July you can expect lower temperatures, the average highest temperature is around 22.65 ℃ (72.77 ℉). At the end of July you can expect lower temperatures, the average highest temperature is around 23.45 ℃ (74.21 ℉). The average number of rainy days in July is 6.3. The average rainfall is 34.7 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 16:35 (hours and minutes), in the middle of the month 16:13 and at the end of the month 15:34.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 United Kingdom in August is this: The average highest temperature in United Kingdom in August is 23 ℃ (73.4 ℉). The average lowest temperature is 14.1 ℃ (57.38 ℉). At the beginning of August you can expect higher temperatures, the average highest temperature is around 23.45 ℃ (74.21 ℉). At the end of August you can expect lower temperatures, the average highest temperature is around 21.45 ℃ (70.61 ℉). The average number of rainy days in August is 8. The average rainfall is 55 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 15:34 (hours and minutes), in the middle of the month 14:45 and at the end of the month 13:50.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 United Kingdom in September is this: The average highest temperature in United Kingdom in September is 19.9 ℃ (67.82 ℉). The average lowest temperature is 11.8 ℃ (53.24 ℉). At the beginning of September you can expect higher temperatures, the average highest temperature is around 21.45 ℃ (70.61 ℉). At the end of September you can expect lower temperatures, the average highest temperature is around 17.7 ℃ (63.86 ℉). The average number of rainy days in September is 8.7. The average rainfall is 49.9 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 13:50 (hours and minutes), in the middle of the month 12:52 and at the end of the month 11:53.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 United Kingdom in October is this: The average highest temperature in United Kingdom in October is 15.5 ℃ (59.9 ℉). The average lowest temperature is 9 ℃ (48.2 ℉). At the beginning of October you can expect higher temperatures, the average highest temperature is around 17.7 ℃ (63.86 ℉). At the end of October you can expect lower temperatures, the average highest temperature is around 13.65 ℃ (56.57 ℉). The average number of rainy days in October is 11. The average rainfall is 62.6 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 11:53 (hours and minutes), in the middle of the month 10:55 and at the end of the month 9:58.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 United Kingdom in November is this: The average highest temperature in United Kingdom in November is 11.8 ℃ (53.24 ℉). The average lowest temperature is 6 ℃ (42.8 ℉). At the beginning of November you can expect higher temperatures, the average highest temperature is around 13.65 ℃ (56.57 ℉). At the end of November you can expect lower temperatures, the average highest temperature is around 10.15 ℃ (50.27 ℉). The average number of rainy days in November is 10.7. The average rainfall is 58.1 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 9:58 (hours and minutes), in the middle of the month 9:05 and at the end of the month 8:22.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 United Kingdom in December is this: The average highest temperature in United Kingdom in December is 8.5 ℃ (47.3 ℉). The average lowest temperature is 3.6 ℃ (38.48 ℉). At the beginning of December you can expect higher temperatures, the average highest temperature is around 10.15 ℃ (50.27 ℉). At the end of December you can expect lower temperatures, the average highest temperature is around 8.3 ℃ (46.94 ℉). The average number of rainy days in December is 9.3. The average rainfall is 47.3 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 8:22 (hours and minutes), in the middle of the month 7:55 and at the end of the month 7:50.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.