Ljubljana - The Environment Agency (ARSO) has issued a red weather alert, its highest, for southern and central parts of the country as some areas have already received more rain in a day than they had in the three summer months.

In a rare occasion ARSO called a press conference on Friday to warn of the risk of floods and more extended downpours locally to follow today in western, central and southern parts of the country and the possibility of powerful storms in particular in the western region of Primorska.

On Thursday, the heaviest rain hit the area between the western town of Idrija and Ljubljana, more precisely the town of Vrhnika to the south-west.

"This area received more rain in 24 hours than in June, July and August combined," weather forecaster Brane Gregorčič said. The amount of rainfall exceeded 200 millimetres in many places.

Record amounts over the past 24 hours have been recorded at Šebreljski Vrh and Idrija in the west of the country, at 258 and 250 millimetres, respectively, Lučine, south-west of Škofja Loka (226ml), Osilnica in the south (210ml) and Vrhnika (208ml).

What has caused problems is mainly stationary convective storms, where heavy precipitation keeps reproducing along certain lines. The process is still happening in that area.

The heaviest rainfall in the area will continue this morning, while in the afternoon the precipitation maximum will slowly spread from the east towards the west and south of Slovenia as colder air moves in, with some weakening in the north-west.

The Kolpa river in the south has already received a large amount of rainfall, but the amount is expected to increase further in the evening and during the night. ARSO warns that the amounts of rain differ hugely between different locations.

The Gradaščica and Poljanska Sora have swollen in their upper parts and have begun flooding. They could rise further in the afternoon if the rainfall increases and extensive flooding is not ruled out.

The Kolpa and some of the tributaries of the Ljubljanica are also expected to spill over during the day, as are streams in the Idrija and Cerkno area and broader parts of central and southern Slovenia.

Most river levels are expected to start receding on Saturday afternoon. During Saturday night, the rivers in the limestone terrain and the lower Sava will reach their highest flows. On Sunday, rivers will be declining throughout the country.

The heavy rain is also causing disruption in traffic with several weather-related accidents reported. Many roads and buildings have been flooded and landslides have blocked some roads.