Heading to camp, cooling off, stormy afternoons, and visiting the ice cream vendor must mean a change of seasons. The northern hemisphere a week ago marked the summer solstice, the day with the most sunlight of the year and the official kickoff for summer. A girl takes a cold shower in order to refresh herself at Ada Ciganlija lake in Belgrade, Serbia, on June 20. The Balkan region is experiencing a heat wave, with temperatures rising as high as 37 degrees Celsius (99 Fahrenheit). A lightning storm rolls across the sky on June 17 in Odessa, Texas. According to the National Oceanic and Atmospheric Administration, which collects its information at the Odessa-Schlemeyer Field, there will be chances of thunderstorms all day Tuesday then returns to sunny skies with the temperature in the mid to high 90s. A boy jumps into the water of a public swimming pool in Hanover, central Germany, on June 17. Meteorologists forecast temperatures up to 30 degrees Celsius and even more for wide parts of the country.