The Mummelsee lies at 1,036 m on the crest of the northern Black Forest, one of the wettest and snowiest places in south-west Germany. It is noticeably cooler than Baden-Baden or the Rhine valley, and the weather can change within an hour. The short answer: late May to early October for walks and boating, December to March if you want snow.
The Mummelsee month by month
Temperatures below are typical daytime highs and night-time lows at about 1,000 m — rough averages, not forecasts.
| Month | Day / night | Crowds | Verdict |
|---|---|---|---|
| January | 0 / −5 °C | Busy on snow days | Snowy and magical; winter sports on the High Road |
| February | 1 / −5 °C | Busy on snow days | Best chance of deep snow; roads can be icy |
| March | 4 / −3 °C | Low | Late snow and thaw; muddy paths |
| April | 8 / 1 °C | Low | Changeable; snow possible, Easter busy |
| May | 13 / 5 °C | Moderate | Fresh green, fewer crowds — a lovely month |
| June | 16 / 8 °C | Moderate | Long days, good hiking, boats running |
| July | 18 / 10 °C | High | Warmest month; busy at weekends |
| August | 18 / 10 °C | High | Summer holidays — come early or late |
| September | 14 / 7 °C | Moderate | Clear days and quieter trails — excellent |
| October | 10 / 4 °C | Moderate | Autumn colours in the valleys; fog possible |
| November | 4 / −1 °C | Low | Grey and quiet; first snow likely |
| December | 1 / −4 °C | Rising | Snow and Christmas markets nearby |
Spring: April to May — waking up
Snow can linger around the lake into April, and paths on the Hornisgrinde are often wet and muddy as it melts. By May the beech woods in the valleys are bright green, the days are long and the crowds are thin. Easter weekend is the exception — expect a busy car park.
Summer: June to August — the main season
This is when the pedal boats run, the terrace is full and the trails are at their best. It is also the busiest time: on sunny weekends and during the German school holidays the car park fills by late morning. The fix is simple — arrive early, or come for the evening light when the day-trippers have gone. Even in July, bring a layer: it is rarely hot at 1,000 m.
Autumn: September to November — our favourite
September and early October bring stable, clear days, some of the best long-distance views to the Rhine plain and the Vosges, and far fewer visitors. The beech and larch in the valleys turn gold in October. From late October, fog and cloud become more common on the ridge — though inversion days, when you stand in sunshine above a sea of fog, are spectacular.
Winter: December to March — snow on the High Road
The northern Black Forest crest is one of the most reliable snow areas in the region. When the snow comes, the lake freezes over, the firs are laden white and small ski lifts and cross-country trails open along the High Road — at Seibelseckle, Mehliskopf, Unterstmatt and Ruhestein. Snowshoe hikes are popular, and a guided snowshoe tour is an easy way to try. Never walk on the frozen lake, and check road conditions before driving up.
When to avoid
- Sunny summer Sundays at midday. Full car park, busy paths.
- Days of dense fog. The lake is atmospheric, but you will see nothing from the Hornisgrinde.
- Icy days without winter tyres. The B500 is cleared, but conditions at 1,000 m can be treacherous.
Christmas markets
From late November to Christmas, Baden-Baden’s Christmas market in front of the Kurhaus and the famous markets of Strasbourg are both within an hour. Combined with a snowy morning at the lake, they make a wonderful winter weekend.
