Like other areas in tropical island, Java Indonesia climate has two seasons: wet season (during October-April) and dry season (during May-September). The dry season is the best time if you want to visit this island. The wettest months are between January-February. West of Java is wetter than Eastern area and mountainous regions receive much higher rainfall. The Parahyangan highlands of West Java receive over 4,000 mm annually, while the north coast of East Java receives 900 mm annually.
The average temperature of Java Indonesia ranging from 22°C to 29°C or about 71.6°-84.2°F. The average of Java Indonesia weather humidity are 75%. The northern area are hotter than middle of the Island, averaging 34°C in the dry season. The south area usually is cooler than the northern area.
Special region of Jakarta has the peaks rainy season in January and February with rainfall 350 millimeters. Jakarta’s average temperature is 27°C. Rainfall between January and early February are very high, that’s when Jakarta was flooded, and the peak dry season in August with an average of 60 millimeters of rainfall. In September and early October are hottest days in Jakata, temperatures can reach 40°C (104°F).
Climate in Banten and West Java region is strongly influenced by Monson Trade and the waves of La Nina or El Nino. When the rainy season the weather is dominated by the West Wind (from Sumatra and the Indian Ocean who joined with winds from Asia through South China Sea), weather is dominated by the East wind which causes the Banten harshed, particularly in the north coast, even more so when the last El Nino. Temperatures in coastal areas ranges between 22°C and 32°C, while temperatures in the mountains with an altitude of between 400-1350 m above sea level between 18°C-29°C. The highest rainfall of Banten province ranging from 2712-3670 mm in the rainy season. In the dry season, the highest rainfall of 615-833 mm in the month of April-December while the lowest rainfall in the dry is 360-486 mm in the month of June to September.
West Java may have temperature of 9°C (48.2°F) at the summit of Mount Pangrango and 34°C (93.2°F) in the North Coast, the average rainfall is 2,000 mm per year, but in some mountainous areas between 3,000 to 5,000 mm per year.
Central area of Java has an annual rainfall average of 2,000 mm per year, and an average temperature of 21-32° C (about 69.8°-89.6° F). Areas with high rainfall mainly located in Nusakambangan island (south of Java), and along the Serayu Mountains. Areas with low rainfall and frequent droughts in the dry season are Blora and surrounding areas as well as in the southern part Wonogiri.
Compared with the western region of Java, East Java has less rainfall. The average rainfall is 1900 mm per year, with the rainy season for 100 days. The average temperature ranges between 21-34°C (about 69.8°-93.2°F). Temperatures in the mountainous areas are lower, and even in Ranu Pani area (slopes of Mount Semeru), temperatures can reach minus 4°C or 24.8°F, which caused a soft snowfall.