Allstate Corp., the second-largest U.S. home and auto insurer, posted its first quarterly loss in more than two years as tornadoes led to a surge in claims costs, Bloomberg reported.

The second-quarter net loss of $620 million compares with a profit of $145 million a year earlier. Catastrophe costs in the second quarter were $2.34 billion, compared with $636 million a year earlier.

More than 1,600 tornadoes have been reported so far this year, compared with 1,282 in all of 2010. Allstate is not unique in dealing with losses from disasters; 2011 has already been the costliest year on record in terms of property damage worldwide, according to a report last month by multinational company Munich Re.