The rainy season in Tibet begins in late June and lasts until early September. The rainy season in Tibet is not as humid as in South Asia, but there are relatively many clouds and rain. If you come to Tibet to see great views of the Himalayas or any other crazy peaks, you have to start after the rain has stopped. You can walk during the rainy season as most of the showers in Tibet occur at night. However, Waterproof clothing and shoes would be nice.