How warm is the Blue Lagoon?
The Blue Lagoon is 37°-40°C (ca. 98°-104°F). The temperature is the same, all year round - summer and winter. If it's windy during winter, the cold winds can cool the water at some locations. However, you will always be able to find a warm spot.
Winter is a great time to spend at Blue Lagoon, floating in the warm water while watching the stars is magical.