Definitely summer is the best time to visit this country because the temperature is the warmest and it is also when more flights are available. The summer is from June until August and the temperatures aren't as cold as they are during the rest of the year, including the winter months. Also, if you come during this time you might be able to see the midnight sun, which is definitely one of the weirdest incidents in the world. Make sure when you visit the country, ensure that you dress properly, even if you are coming during the summer because if you are taking a cruise the wind can make it feel much colder than it actually is. Also, during winter season make sure that you are wearing plenty of layers so that you can keep warm and don't get sick because of the cold.