Personal lines insurer Allstate expects the May catastrophic pre-tax losses to be $600m for the month of May 2011, bringing the total catastrophe pre-tax loss to $2bn, for the second quarter months of April and May 2011.
According to the Allstate, the estimated May catastrophe losses comprised seven events.
Previously, the insurer estimated a pre-tax catastrophe losses of $1.4bn for the month of April 2011.
The insurer said the releases of loss estimation is part of its previously announced plan to provide the updates whenever a monthly estimate exceeds $150m.
The rise in claims are in result of a series of severe tornadoes that caused the extensive damage in Alabama, Missouri and over a dozen other states.
Earlier, the catastrophe modeling firm AIR Worldwide has estimated the total insured losses from the severe thunderstorm that hit the US from May 20-27, to cause between $4bn and $7bn.