Third-quarter results are rolling in, and the theme remains the same as it has been throughout the year: Catastrophe losses are dragging down profits.

Allstate Corp. says 2011 third-quarter net income dropped 55 percent to $165 million on about $1.1 billion in catastrophe losses from 23 loss events. The Northbrook, Ill.-based insurer posted 2010 third-quarter net income of $367 million, during which it took catastrophe losses of $386 million.

Catastrophes during this year’s third quarter, including Hurricane Irene and Tropical Storm Lee, contributed 16.7 points to the company’s property-liability combined ratio of 104.8—an increase of 8.9 points from Allstate’s combined ratio during the third quarter a year ago.

W.R. Berkley Corp. says its third-quarter net income was down 18.1 percent to $77 million, compared to $94 million during the same period a year ago.

Catastrophe losses were $51 million during the third quarter compared to $22 million during the same time in 2010.

Net income for the first nine months is down 14 percent for the company, to about $276.9 million. For the first nine months of 2011 and 2010, catastrophe losses were $139 million and $75 million, respectively, the commercial insurer says.

Chicago-based specialty insurer CNA Financial Corp. reports third-quarter net income of $75 million, compared to a net loss of $140 million a year ago.

Though net written premiums grew 8 percent, the company’s property-and-casualty operations saw $32 million in after-tax catastrophe losses and net-realized investment results decreased $56 million to a loss of $16 million compared to the 2010 third quarter, CNA says.

Net operating income increased to $91 million from a loss of $158 million a year ago when CNA sold its legacy asbestos and environmental-pollution liabilities to Berkshire Hathaway’s National Indemnity Co.

Without the loss associated with the portfolio transfer, CNA says third-quarter operating income dropped $95 million compared to the same period in 2010.

ACE Ltd. reports a $31 million third-quarter loss and says catastrophe losses were $121 million, compared to $97 million during the same time in 2010.

ACE says financial-market volatility in the credit, equity and foreign-exchange markets also impacted third-quarter net income. The volatility affected ACE’s variable-annuity reinsurance business, resulting in a $660 million net loss for that line.

In a statement, Evan Greenberg, ACE’s chairman and CEO, blamed a “historic drop in interest rates—the lowest level in over 100 years,” he said, as well as other factors for the results.

A year ago during the third quarter, ACE reported net income of $675 million.

American Financial Group Inc. says it was able to avoid large catastrophe losses in the quarter due to the company managing its wind-exposed business, but, like ACE, low interest rates and national and global economic uncertainty took their toll. The company says third-quarter net income was down 27.3 percent to $96 million compared to the same time a year ago.

Bermuda-based insurers and reinsurers also report catastrophe-impacted results for the quarter.

Everest Re says third-quarter net income dropped 64 percent to $63 million compared to a year ago, driven mainly by $119 million in catastrophe losses. The losses include $35 million for Hurricane Irene as well as increased loss estimates on first-quarter losses related to the earthquakes in Japan and New Zealand.

In the 2010 third quarter, the company reported $89 million in catastrophe losses.

Montpelier Re says it took a third-quarter net loss of $66 million, compared to net income of $90 million a year ago. The company saw $60 million in catastrophe losses, with $30 million coming from Hurricane Irene, Texas wildfires and other U.S. events.

Endurance Specialty Holdings says it took a $20 million loss in the quarter compared to net income of $139.1 million a year ago, driven by catastrophe losses of $91.1 million in its reinsurance segment. The cat losses account for 37.6 points to the reinsurance segment’s 115 combined ratio.

Aspen Insurance Holdings says third-quarter net income was $22.2 million, a 76.1 percent drop from a year ago. The company saw $55 million in losses from third-quarter catastrophes and adjustments to previous losses.

Validus Holdings says net income fell 76.3 percent to $56.5 million in the quarter. Losses from weather and other events for the quarter were $51.9 million, which caused a $47.9 million decrease to net income.

Rounding out the Bermuda companies, Arch Capital Group Ltd. saw a 14.75 percent increase in third-quarter net income, to $162.5 million, despite catastrophe losses of $59.6 million, net of reinsurance and reinstatement premiums.