The Midnight sun is a natural phenomenon that occurs in the north pole within Arctic Circle. This phenomenon occurred during the summer months in Rovaniemi. The midnight sun is referred to the day that sun visible all day and did not rest.
Midnight sun creates white night, which is a commonly known term in Saint. Petersburg, Russia, and this occurrence happens as well in the north of the Arctic Circle and the South of the Antarctic Circle. This phenomenon lasts for nearly a month in Rovaniemi every year. Due to 24 hours of sunlight per day, this is the most active time of the year and base on that, Finnish has a holiday called Midsummer festival ( Juhannus ), which celebrate the longest bright time of a year, that usually occur on 21st or 22nd of June. This is a very characteristic and unique event in Finland. Make sure you save the date to witness it!
(Source: Instagram: VeryFinnishproblems)