Storms in Central Europe, Canada and India fueled about $27 billion in flooding-related economic losses in June, as the damage in one month exceeded the 10-year average for the first half of a year.

Flooding caused about $22 billion in economic losses in Europe and $3.8 billion in Canada, Aon Plc’s Impact Forecasting said today in a report. The average flooding cost for the first six months of a year is about $20 billion, Steve Bowen, a senior scientist and meteorologist at Impact, said in an interview. This year the total is $37.8 billion through June 30, he said.

“It’s definitely not the norm” to have costs of more than $25 billion in a month, said Bowen. While surges from tropical storms are often associated with the worst floods, the June catastrophes “have all been as a result of exceptionally heavy rainfall that prompted major rivers and their tributaries to overflow in densely populated areas,” he said.

At least 23 people were killed in Europe from flooding that began in late May, Impact said. Insured losses on the continent may be as high as $5.3 billion, with most of the costs in Germany, according to the statement. Flooding in Calgary last month contributed to costs for insurers of up to $1 billion in Canada, Impact said.

Chubb Corp. is among insurers that suffered flooding-related losses in the period. The firm slumped $1.60, or 1.8 percent to $85.40 at 2:25 p.m. in New York, the biggest decline in the 22-company Standard & Poor’s 500 Insurance Index. The Warren, New Jersey-based company said late yesterday that disasters including U.S. storms and Canada flooding cost $156 million after tax, or 60 cents a share, in the second quarter.

Insured losses for the industry in June may be as much as $500 million from monsoon rainfall in India and Nepal. Economic losses were at least $1.1 billion according to Impact, which said more than 5,000 people were reported dead or missing.

Costs still trailed the first half of 2011 when there were losses of about $55 billion due to events in Australia, China, Colombia and the U.S., Bowen said.