The annual average temperature in most areas of Hainan is between 22.5-25.6℃, the central mountain area is slightly lower than 23℃, and the southern and western regions are slightly higher than 25℃. The isotherm is curved to the south in an arc, increasing from the central mountainous area to the coast. The coast is higher than the inland and the south is higher than the north. The coldest month is January, and the monthly average temperature in the central mountainous area is about 16.5°C, the lowest in the island. Most areas of the hottest month occur in July, and the average monthly temperature in Dongfang City is 29.2℃, the highest in the island.