The climate is subtropical in the north and tropical in the south, with average annual temperatures of 22 degrees Celsius (72 degrees Fahrenheit) in the north and 24 degrees C. (75 degrees F.) in the south. Summers, which last from May through September, are usually hot and humid, with average daytime highs from 27 to 34 degrees C. (81 to 93 degrees F.). Winters, from December through February, are short and mild, with average lows from 12 to 17 degrees C. (54 to 63 degrees F.); snow falls only on the higher mountains. Except for mountain areas, the mean monthly temperature in winter is above 15C.

The mean annual rainfall is 2,580 mm (103.2 inches) per year, with a maximum of more than 6,000 mm (211.2 inches). In winter a northeasterly monsoon brings heavy rains to the eastern and northern sides of the island, while in the summer, in the face of the prevailing southwesterly monsoon, the central and southern parts have more rain than the north. Thunder showers and typhoons often bring Taiwan heavy rainfall in summer months.