Complex sentence: From May to September, the mountain areas are normally warm and dry with temperatures reaching 80--90 ° F in mid-summer, though the weather is still highly variable, with many days of fog and light rain.
Split into simpler sentences: From May to September, the mountain areas are normally warm and dry with temperatures reaching 80 °-90 ° F in mid-summer. Though the weather is still highly variable, with many days of fog and light rain.