The best time to visit Altena depends on your preferences for weather and activities, but generally, late spring (May-June) and early autumn (September-October) offer the most pleasant conditions.During late spring, the weather is typically mild and sunny, great for exploring the outdoors. The surrounding Märkischer Kreis region is lovely with blooming flowers and lush greenery, making it ideal for walking or cycling along the Lenne River. Temperatures are comfortable, usually ranging from 15°C to 20°C, which is great for visiting Altena Castle or wandering through the town's historic streets without the intense heat of summer.Early autumn also provides excellent conditions. The weather remains comfortable, with average temperatures between 10°C and 18°C, and the landscape transforms with beautiful autumnal colours. This period is particularly good for those who enjoy photography or prefer a quieter experience, as the peak summer tourist crowds have usually dispersed. You can still enjoy outdoor activities, and the town's museums and cafes offer a warm retreat on cooler days.For those who prefer warmer weather and don't mind larger crowds, the summer months of July and August can also be a good choice, with temperatures often reaching 20°C to 25°C. However, these months can also see more rain.