A sunny weekend by car is the trip people most often get wrong in both directions. They drive five hours for weather they could have had in ninety minutes, or they expect a 300 km radius to turn Hamburg into Lisbon. Distance is not a climate.
The useful question is what kind of weather sits inside the hours you are willing to spend behind the wheel, starting from your front door.
Two limits, before the destination
Daylight. In late June a four-hour round trip still leaves a long day. In late December the same drive can leave you two hours of grey light at the other end. If the usable time falls under about three hours, stay the night or pick somewhere closer. The sums are in day trip or overnight.
The same weather system. Cloud, rain and a cold pool cover hundreds of kilometres. If the whole of your driving radius is under one grey sky, the sunniest town on the list is a rounding error. Going further by car that weekend will not help. You either fly, or you wait.
A practical cap for a weekend, if you want some of Saturday at the destination, is about three to four hours of driving each way. That is often somewhere around 250–350 km on ordinary roads, and more on a clear motorway. It is not a rule of physics. It is the point at which the drive starts to be the holiday.
What that radius usually contains
It depends entirely on where you start. The same 300 km is a different product in Munich and in Amsterdam.
From the Alps’ north side — Munich, Salzburg, Innsbruck. In summer this is one of the best car radii in Europe. A few hours reaches the Alpine valleys when the foreland is stormy, and a longer day reaches Lake Garda or the top of the Adriatic, which really can be warmer and brighter. In winter the same drive often goes somewhere colder. The mountains are not a winter-sun escape. That trip is a flight, described in where to find sun from Munich.
From the Low Countries and the north German plain. The coast, the Ardennes and the nearer German uplands are reachable. They are pleasant. They are rarely a different season from home. A “sunnier” result of one extra hour, with the same temperature, is usually not worth a full tank of fuel. The interesting weather starts at flight distance: the Mediterranean, and in winter the Canaries or further south.
From northern Italy or the south of France. You may already be in the good weather. A drive then is for a coast, a hill town or a lake, not for a transformation. If home is 30 °C and sunny, the ranking has nothing useful to sell you except somewhere cooler.
From Britain. The sunny weekend by car is the hardest version. The island is small and the weather is shared. The south coast can be brighter than Scotland; it is not a winter beach. The first trip that changes the climate is usually a flight or the tunnel plus a long drive into France, which has stopped being a relaxed weekend. More on that in where to find sun from London.
Summer, winter, and the weekends in between
April to June, and September. This is when a car weekend pays most often. The south of your radius — a coast, a lake, a valley with a drier climate — can be a different day from a cloudy home, without the heat of August. Spring and autumn guides cover the regions. Your radius decides which of those regions exist for you.
July and August. Sun is easy to find and easy to have too much of. Driving south can mean driving into a hotter version of a day you already had. Look at the temperature, not only the sun icon. Somewhere higher, or on a cooler coast, can be the better result.
November to February. Do not expect the car to find a beach. It can find a bright frost, a city with better light, or a valley that is simply less grim. If the goal is 20 °C, you are in the wrong vehicle. See winter sun you can actually reach.
Before you set off
Check the way back as well as the destination. A sunny Saturday and a wet Sunday drive through roadworks is a different weekend from the forecast screenshot. Mountain routes add weather of their own: a pass can be fine in the valley forecast and closed in practice.
Then compare the destination with home, not with an ideal. If home is already the best day of the week, a prettier place with the same forecast is a scenery trip. Say that honestly and go for the scenery, or stay.
See what this weekend looks like within 300 km. If the verdict is that nothing beats home, believe it. The car will still be there when the pattern changes.