Best Time to Visit Longyearbyen
The best time to visit Longyearbyen really depends on what you're most excited to do.
Between May and September, during the summer, you'll have the highest chance to see polar bears and other arctic wildlife because this is when the ice begins to melt and ships can begin to access otherwise inaccessible places around Longyearbyen. Additionally, unlike in the winter in Longyearbyen, there will be plenty of light which will assist you greatly when viewing wildlife. During these summer months is also usually considered the best time to try a variety of activities including sledding, skiing, dog sledding, and hiking due to the warmer temperatures and the fact that there will be light.
Between October and February most of the archipelago is frozen over and there is little-to-no light for these months and this is called the Polar Night. This is by far the best time to see the Northern Lights (Aurora Borealis) which is a truly life-changing sight. The Polar Night comes to an end towards the middle of February most years, so you'll have the opportunity to do activities during that time.
Between March and April is a good time to come if you only are interested in experiencing light snow and sporty activities. It's not a peak time for wildlife and the Northern Lights are hard to spot during these months. But during this time of year you'll be able to take in the scenery through a variety of activities with very few crowds and without being too cold.