The islands have a hot, rainy season from November to April and a cool, dry season from May to October. The rains accumulate 2,500 to 3,000 millimetres (98–118 in) each year. The average humidity is 80% and the temperature 26.6 °C (79.9 °F).Only five percent of the islands' land area is arable land; permanent crops cover another 20%. Deforestation (only small portions of the original forests remain), largely as a result of the continued use of wood as the main fuel source, is a serious problem; as a consequence of cutting down the forests, the mountainous terrain of Futuna is particularly prone to erosion. There are no permanent settlements on Alofi because of the lack of natural fresh water resources. The two island groups lie about 260 km apart: