Do you need to know, when is the best time to go to Schleswig-Holstein? Then you should take a look here, what weather you can expect there during the year.
Schleswig-Holstein is part of Germany. Germany is quite a large country, so the climate is diverse. Generally the climate of Germany is temperate, it is marine in the north. You can expect cool, sometimes cloudy and wet winters, and mild summers. You would probably expect a warmer climate in the south, but don't forget the Alps, which prevent much of the warmer Mediterranean air to blow up into southern Germany. Weather in Alps is usually colder than in lowlands, of course. And it is often very cold at the peaks.
When speaking about the usual weather in this area, the information is relevant for example for these popular places: Amrum, Bad Segeberg, Fehmarn, Flensburg, Föhr, Grömitz, Heligoland, Holstein Switzerland, Itzehoe, Kiel, Lübeck, Neumünster, North Frisian Islands, Pellworm, Plön, Rendsburg, Sankt Peter Ording, Sylt, Travemünde, Wedel.
Let's look now what weather you can expect in the area around Kiel and in many other cities. The warmest month here is July, the average maximum temperature is 21.6 ℃ (70.88 ℉). The average minimum temperature in this month is 13 ℃ (55.4 ℉). The coldest month here is January, the average maximum temperature is 4.6 ℃ (40.28 ℉). The average minimum temperature in this month is 0.2 ℃ (32.36 ℉). The most rainy month here is January, the average number of rainy days is 12.7. The least rainy month here is May, the average number of rainy days is 7.9. 
When travelling around Schleswig-Holstein, always consider the altitude of the the place as well. We should remind you, that the highest point in Germany is Zugspitze (2963 m) and the lowest point is Neuendorf bei Wilster (-3 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 Schleswig-Holstein in January is this: The average highest temperature in Schleswig-Holstein in January is 4.6 ℃ (40.28 ℉). The average lowest temperature is 0.2 ℃ (32.36 ℉). At the beginning of January you can expect higher temperatures, the average highest temperature is around 4.8 ℃ (40.64 ℉). At the end of January you can expect higher temperatures, the average highest temperature is around 5 ℃ (41 ℉). The average number of rainy days in January is 12.7. The average rainfall is 73 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 7:23 (hours and minutes), in the middle of the month 7:53 and at the end of the month 8:42.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 Schleswig-Holstein in February is this: The average highest temperature in Schleswig-Holstein in February is 5.4 ℃ (41.72 ℉). The average lowest temperature is 0.6 ℃ (33.08 ℉). At the beginning of February you can expect lower temperatures, the average highest temperature is around 5 ℃ (41 ℉). At the end of February you can expect higher temperatures, the average highest temperature is around 6.6 ℃ (43.88 ℉). The average number of rainy days in February is 11.8. The average rainfall is 51.5 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 8:42 (hours and minutes), in the middle of the month 9:42 and at the end of the month 10:46.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 Schleswig-Holstein in March is this: The average highest temperature in Schleswig-Holstein in March is 7.8 ℃ (46.04 ℉). The average lowest temperature is 1.7 ℃ (35.06 ℉). At the beginning of March you can expect lower temperatures, the average highest temperature is around 6.6 ℃ (43.88 ℉). At the end of March you can expect higher temperatures, the average highest temperature is around 9.85 ℃ (49.73 ℉). The average number of rainy days in March is 11.7. The average rainfall is 61.4 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 10:46 (hours and minutes), in the middle of the month 11:52 and at the end of the month 12:58.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 Schleswig-Holstein in April is this: The average highest temperature in Schleswig-Holstein in April is 11.9 ℃ (53.42 ℉). The average lowest temperature is 4.1 ℃ (39.38 ℉). At the beginning of April you can expect lower temperatures, the average highest temperature is around 9.85 ℃ (49.73 ℉). At the end of April you can expect higher temperatures, the average highest temperature is around 13.95 ℃ (57.11 ℉). The average number of rainy days in April is 8.6. The average rainfall is 42 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 12:58 (hours and minutes), in the middle of the month 14:04 and at the end of the month 15:06.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 Schleswig-Holstein in May is this: The average highest temperature in Schleswig-Holstein in May is 16 ℃ (60.8 ℉). The average lowest temperature is 7.4 ℃ (45.32 ℉). At the beginning of May you can expect lower temperatures, the average highest temperature is around 13.95 ℃ (57.11 ℉). At the end of May you can expect higher temperatures, the average highest temperature is around 17.4 ℃ (63.32 ℉). The average number of rainy days in May is 7.9. The average rainfall is 44.9 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 15:06 (hours and minutes), in the middle of the month 16:02 and at the end of the month 16:46.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 Schleswig-Holstein in June is this: The average highest temperature in Schleswig-Holstein in June is 18.8 ℃ (65.84 ℉). The average lowest temperature is 10.3 ℃ (50.54 ℉). At the beginning of June you can expect lower temperatures, the average highest temperature is around 17.4 ℃ (63.32 ℉). At the end of June you can expect higher temperatures, the average highest temperature is around 20.2 ℃ (68.36 ℉). The average number of rainy days in June is 11.3. The average rainfall is 70.8 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 16:46 (hours and minutes), in the middle of the month 17:11 and at the end of the month 17:10.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 Schleswig-Holstein in July is this: The average highest temperature in Schleswig-Holstein in July is 21.6 ℃ (70.88 ℉). The average lowest temperature is 13 ℃ (55.4 ℉). At the beginning of July you can expect lower temperatures, the average highest temperature is around 20.2 ℃ (68.36 ℉). At the end of July you can expect lower temperatures, the average highest temperature is around 21.5 ℃ (70.7 ℉). The average number of rainy days in July is 11.2. The average rainfall is 89.2 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 17:10 (hours and minutes), in the middle of the month 16:44 and at the end of the month 15:59.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 Schleswig-Holstein in August is this: The average highest temperature in Schleswig-Holstein in August is 21.4 ℃ (70.52 ℉). The average lowest temperature is 12.7 ℃ (54.86 ℉). At the beginning of August you can expect higher temperatures, the average highest temperature is around 21.5 ℃ (70.7 ℉). At the end of August you can expect lower temperatures, the average highest temperature is around 19.6 ℃ (67.28 ℉). The average number of rainy days in August is 10. The average rainfall is 71.2 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 15:59 (hours and minutes), in the middle of the month 15:03 and at the end of the month 14:01.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 Schleswig-Holstein in September is this: The average highest temperature in Schleswig-Holstein in September is 17.8 ℃ (64.04 ℉). The average lowest temperature is 10.4 ℃ (50.72 ℉). At the beginning of September you can expect higher temperatures, the average highest temperature is around 19.6 ℃ (67.28 ℉). At the end of September you can expect lower temperatures, the average highest temperature is around 15.4 ℃ (59.72 ℉). The average number of rainy days in September is 11.3. The average rainfall is 73.9 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 14:01 (hours and minutes), in the middle of the month 12:57 and at the end of the month 11:52.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 Schleswig-Holstein in October is this: The average highest temperature in Schleswig-Holstein in October is 13 ℃ (55.4 ℉). The average lowest temperature is 6.7 ℃ (44.06 ℉). At the beginning of October you can expect higher temperatures, the average highest temperature is around 15.4 ℃ (59.72 ℉). At the end of October you can expect lower temperatures, the average highest temperature is around 10.2 ℃ (50.36 ℉). The average number of rainy days in October is 11.4. The average rainfall is 73.2 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 11:52 (hours and minutes), in the middle of the month 10:47 and at the end of the month 9:43.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 Schleswig-Holstein in November is this: The average highest temperature in Schleswig-Holstein in November is 7.4 ℃ (45.32 ℉). The average lowest temperature is 2.7 ℃ (36.86 ℉). At the beginning of November you can expect higher temperatures, the average highest temperature is around 10.2 ℃ (50.36 ℉). At the end of November you can expect lower temperatures, the average highest temperature is around 6.2 ℃ (43.16 ℉). The average number of rainy days in November is 10.6. The average rainfall is 57.7 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 9:43 (hours and minutes), in the middle of the month 8:44 and at the end of the month 7:55.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 Schleswig-Holstein in December is this: The average highest temperature in Schleswig-Holstein in December is 5 ℃ (41 ℉). The average lowest temperature is 0.6 ℃ (33.08 ℉). At the beginning of December you can expect higher temperatures, the average highest temperature is around 6.2 ℃ (43.16 ℉). At the end of December you can expect lower temperatures, the average highest temperature is around 4.8 ℃ (40.64 ℉). The average number of rainy days in December is 11.8. The average rainfall is 76 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 7:55 (hours and minutes), in the middle of the month 7:24 and at the end of the month 7:18.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.