Complex sentence: Summer daytime averages according to Weatherbase all three major urban areas are on average around with daytime winter temperatures hovering around the freezing point, with slightly colder nights averaging in Jönköping rendering its continental classification.
Split into simpler sentences: Summer daytime averages are similar throughout the province, since according to Weatherbase all three major urban areas are on average around with daytime winter temperatures hovering around the freezing point. The slightly colder nights averaging in Jönköping are rendering its continental classification.