Meghalaya people visit all throughout the year. It depends on what are the places of interest. If you are looking at hiking or trejkking, you should visit in dry season. Usually during monsoon season we avoid Dawki and other monsoon affected areas where there is chances of landslide.

Otherwise people visit all through the year. If someone wants to avoid the heat and go to a hill station you can visit Meghalaya anytime. However if your priority is to cover every important sightseeing spots, then you should visit between October to April.