The best time to do the Rupin pass trek is either the summer season ( May and June) or the post-monsoon period( Sept to October). The summer months are the best times if you want to witness snow on the trail.
The temperatures also remain relatively normal during these times. You can also expect some light showers. This is also the season when rhododendrons bloom all over along this trail.
Planning a trip during monsoons should be avoided as heavy rains can cause rivers to overflow and cause landslides. Also, the terrain becomes muddy and slippery.
The post monsoons period is absolutely hassled free if you are planning the trek.The sky is clear and the weather is perfect. The monsoons transform the landscape, making it verdant and green. Wildflowers that grow in the valleys along the trekking route also remain till September.
Ideally temperatures during the day range from 13 to 18 degree Celsius and 0-7 degrees Celsius during the night. During winters the temperatures drop further.