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he Bali bureau of the Meteorology, Climatology and Geophysics Agency (BMKG) announced Friday that residents of the resort island should be on alert for the possibility of tornados and lightning from active cumulonimbus clouds. The clouds are formed by atmospheric instabilities as the island experiences a transition from the rainy to the dry season. The period spans from March until May.

"It is not a certain thing, but active cumulonimbus clouds could possibly bring a tornado and lightning to any area beneath them. Therefore, people must be aware and cautious of such clouds," BMKG's data and information officer Endro Tjahjono said Friday, adding that a small tornado had hit Ubung bus station in Denpasar recently.

Tjahjono further explained cumulonimbus clouds usually formed in the afternoon, following a bright and clear day.

Cumulonimbus clouds are characterized by their vertically growing, dense cloud formations. They range in color from brownish, to grayish to deep black and carry thunderstorms.

These clouds can form alone, in clusters, or along a cold front in a squall line. They create lightning through the heart of the cloud. Cumulonimbus clouds appear from cumulus clouds and can further develop into a super cell, which carry severe thunderstorms.

Rain and lighting hit parts of Denpasar at dawn on Friday.

"The top part of the cloud has a mushroom-like shape. The clouds carry lightning, which could affect an area of five to 10 square kilometers beneath," he added.

He strongly suggested the island's residents refrain temporarily from conducting any activity on open fields, from sheltering under tall trees or from standing near any electrical poles or stations as cautionary measures against the dangers of lightning.

In the last couple of days the island's residents also have had to cope with blistering heat. This uncomfortable climate is the result of the particular position of the sun during the transitional period.

Tjahjono explained that the sun was directly above the equator on Monday. The hot weather is expected to last the next few days.

"The sun was precisely above the equator line on Monday. This condition will surely increase the temperature during and several days after that phenomenon," he said, reminding that Indonesia lies directly below the celestial equator.

According to BMKG staff member Tofan Primadi, Friday's temperature ranged between 23 and 33 degrees Celsius with humidity of between 58 and 90 percent.

"The hottest day was Wednesday, when the temperature reached 34 degrees Celsius with humidity of between 55 and 88 percent," he said.