Trekking to Mardi Himal is double throughout the year. However, some seasons are the best time to visit there in terms of the BEST weather. In terms of weather, autumn and Spring are the best time to visit the Mardi Himal Trekking due to stable and clear weather. But this season might not be the best for those who are looking for less busy ( less crowded ). As Autumn and Spring are the best seasons, there will be huge traffic in Mardi Trekking. If you want to avoid this somehow, you can make the trip some weeks ago before this season starts or some weeks later after the best seasons.
In September, Early September might not perfect (depends on the weather) to visit this trail due to post-monsoon. However, generally, we can get good weather from mid of September. You can see the best view of Annapurna and the fishtail. Moreover, it is not a busy season. Hence you will get more hospitality from the teahouses.
December is also considered the best time to trek due to favourable weather for viewing the sights. It will be cold in the morning and evening outside of teahouses but during the day, the temperature might be suitable to hike the base camp of Mardi. Traffic will get less than the peak (October to November). Hence December is also the best time for Mardi Himal Base Camp Trekking.
In conclusion, if you are looking for the best time to visit Mardi Himal in terms of weather as well as less traffic, mid of February to Early June and mid-September to Early October is the best month to visit Mardi Himal Base Camp Trekking.
If you are searching for the best trekking company for the Mardi Himal Trek, Base Camp Hike is one of the best trek company for the Mardi Himal Trek along with other treks in Nepal.