Why does this happen? The Earth is tilted on its axis. As it spins around the sun once a year, the top of the world leans towards the sun in our summer and away from it in our winter. The further north you go, the bigger that effect gets.
In Tromsø, a city in the far north of Norway, the sun stays above the horizon for about two months in summer without ever setting. People play football at midnight in full sunshine. To sleep, they pull thick black curtains across the windows so the bedroom feels like night.
In midwinter, the opposite happens. The sun doesn't rise at all for almost two months. The sky goes light grey around the middle of the day, but the sun never quite climbs over the horizon. Children walk to school in the dark and home in the dark. Streetlights stay on all day, and people light extra candles in their homes to feel cosy.
Norwegians have a word for this winter cosiness: koselig. It means warm, snug and content - like hot chocolate, blankets, candles and good company. The dark season is hard, but families and schools fill it with light, songs and time together.