Dieng Plateau Freezes Over, Temperatures Drop to Minus 1 Degree Celsius

The Arjuna Temple complex in Dieng Kulon Village, on the Dieng Plateau in Banjarnegara Regency, Central Java, has frozen over and been blanketed by frost. The phenomenon of dew frost, locally called bun upas, has enveloped the Dieng area over the past few days with the arrival of the dry season, causing temperatures there to touch minus 1 degree Celsius. Dieng Kulon Village Secretary Sabar Alfarisi said the frost began appearing several days ago as air temperatures continued to drop at night and into the morning. “The frost has been appearing for roughly the last three days in Dieng. Its distribution is visible around the Arjuna Temple complex and several other open areas,” he said on Tuesday afternoon. According to him, this natural phenomenon, a hallmark of the dry season in Dieng, always attracts tourist attention. Consequently, many visitors have arrived since the early hours to witness and capture images of the thin ice crystal layers forming on grass and plant surfaces. “Many tourists have already come to see and photograph the frost. This phenomenon is always a special attraction for visitors to Dieng,” he said. Head of the Meteorology, Climatology and Geophysics Agency (BMKG) Central Java Climatology Station, Goeroeh Tjiptanto, said this year’s bun upas was triggered by dry weather conditions over recent days. Based on BMKG data, he said, rainfall in the Dieng area from 6 to 9 June 2026 was recorded at 0 millimetres. “Zero millimetres of rainfall indicates the atmosphere is in a very dry condition. Additionally, the sky tends to be clear and cloudless from night until morning,” he said. He explained that the absence of cloud cover allows heat stored on the earth’s surface during the day to be released maximally into the atmosphere and outer space at night. According to him, this condition causes the cooling process to occur rapidly, so ground surface temperatures drop drastically. “Based on data, the minimum air temperature in Dieng on 9 June 2026 reached 1.05 degrees Celsius at 01.01 WIB. Meanwhile, the grass or ground surface temperature was recorded even lower, at 0.60 degrees Celsius at 08.30 WIB,” he said. He stated these conditions enable the formation of thin ice crystal layers on grass, agricultural crops, and other surfaces directly exposed to the cold air. He said Dieng’s topography, which is a basin surrounded by mountains, further strengthens the formation of frost. “Cold air from the mountain slopes moves downwards at night and becomes trapped at the valley floor, making temperatures in the area much lower than surrounding regions,” he said. In relation to this, Goeroeh urged residents and tourists visiting Dieng to prepare warm clothing and be aware of the extreme cold temperatures, which are expected to potentially persist over the next few days, especially at night and into the morning.