
The seasons in Iceland are very different from another with summer, autumn, winter and spring. The tourism can be divided to summer season and winter season.
In summer you have many companies offering various activities but in winter many of these companies will simply close. There is less birdlife, and many activities is impossible to operate when everything gets frozen. The Companies that are open focus on ice cave tours, northern light tours and a few other options.
In spring you can have the situation that companies have stopped offering their winter option tours but at the same time summer tours are not available.

For many people in the tourism sector April and May is often the best change to take holiday as this is somewhat slower in traffic.
For the Fjallsárlón iceberg boat tour this time if waited with anticipation. The lagoon is frozen during winter but is slowly starting to melt in March. Boats are being made ready and all engines tested.
Even for the most experienced guide the feeling of getting back on water in Fjallsárlón is always joyful.
Iceland has a habit of tricking you once or twice about the arrival of spring. You might have days like warm summer days in March or April but a snowstorm and minus 6 the day after.
This of course results in uncertainty and challenges operating the tours but still the iceberg boat tour has been offered in beginning of April for years.

You can be getting the best things of two worlds arriving in April, seeing northern lights and getting a warm sunny day doing a boat tour and ice cave tour in Fjallsarlon. There is low traffic of other tourists and prices for accommodation is lower during this period. Since the traffic is low you can most likely also have some flexibility in your planning which is wise to do as you can expect storms in parts of the country in April. To make the most out of your travel and not allow weather to interfere with your tours planned it can be wise to switch days with some of your activities.