Due to the city's high northerly latitude, the length of the day varies widely from more than 18 hours around midsummer to only around 6 hours in late December. The nights from late May until mid-July are bright even when cloudy. Stockholm has relatively mild weather compared to other locations at a similar latitude, or even farther south. With an average of just over 1800 hours of sunshine per year, it is also one of the sunniest cities in Northern Europe, receiving more sunshine than Paris, London and a few other major European cities of a more southerly latitude. Because of the urban heat island effect and the prevailing wind traveling overland rather than sea during summer months, Stockholm has the warmest July months of the Nordic capitals. Stockholm has an annual average snow cover between 75 and 100 days.