Why is most construction work in Alaska done in summer?

Actually, once the cold winter days give way to warm summer ones, construction tends to pick up thanks to the long hours of daylight. Some places can experience between 17 and 24 hours of daylight during the summer months making for long work days and great opportunities for overtime

This is down to the longer hours of daylight in the summer months and the warmer temperatures.

This is when land is most accessible

It's because of the weather and temperature in Alaska. It gets incredibly cold being near the arctic