THE HAGUE (AFP) - Heavy storms swept the Netherlands on Thursday (June 23), leaving one man dead after he was electrocuted in his flooded cellar where he was growing cannabis, police and media said.

The Dutch national weather centre posted an orange alert warning of further flooding from "thunderstorms and heavy rainfall" as insurers estimated there had already been some 20 million euros in damage.

The 45-year-old man was found lying in water in the basement of his Rotterdam home early on Thursday as violent storms battered the west of the low-lying country, the police said.

"He was killed by electrocution," the Rotterdam police said in a statement, indicating that they had opened an investigation but noting that the emergency services had "found cannabis (plants) in the cellar."

The bad weather, which hit the west and centre of the country early on Thursday, was to continue for much of the day, with the Dutch national weather service (KNMI) warning of further severe thunderstorms accompanied by hail and high winds.

In Rotterdam, some 26mm of rain fell in just 20 minutes early Thursday, the public broadcaster NOS reported.

The central town of Randstad was particularly badly hit, with the Dutch Association of Insurers estimating it had suffered some 20 million euros in damage.

"It's a conservative estimate," a spokesman for the association told the Dutch news agency ANP.