Slovakia's climate is split by the mountain ranges at its heart. The Danube lowland across the southwest is the nation's warm spot. Enough moisture trickles up from the Mediterranean so that many days in July and August feel a touch humid across the plains and on the Danube (where Bratislava and Vienna share a similar climate). The rest of Slovakia is similarly warm by day but a bit cooler at night, especially in the highlands. Summer is the wettest season in this not too wet part of Europe. The warm-season thunderstorms wane in September and October, just in time for people to take advantage of the still-mild temperatures and sunny days. A second surge of moisture late in the autumn often brings a few spells of dreary, damp weather before winter sets in. Cold air masses sometimes camp out in the valley tucked between two arms of the Carpathians: towns like Presov and Kosice may be subjected to dank fog and snow flurries for days at a time. It's more conventionally wintry in Bratislava, with a few bitterly cold days, but some mild ones as well. Higher terrain, including the Tatra range, is generally colder than the Danube valley. Points at elevation may get a hefty covering of snow (and sudden thunderstorms in the summer); passes in the High Tetras may be snowcovered as early as September. However, on average there's more mid-winter sun at altitude than in the clouded-over lowlands of the east.