(Sharecast News) - Bad weather hit first half operating profits at insurer RSA which reported a 15% fall to £304m.Underwriting profit fell 23% to £171m, with group weather costs elevated at 4.9% versus a benign prior year of 1.2%. Net written premiums fell 5% to £3.2bn on a constant currency basis and the combined ratio weakened to 94.7% from 93.2% in 2017.The interim dividend was increased 11% to 7.3p a share.Group weather costs were £155m or 4.9% of net earned premiums with Canada the most affected region with a weather ratio of 10%, twice the annual five year average, RSA said."In particular, at a cost to the industry of more than $500m, the windstorm of early May is likely to be the most costly insured event in Ontario and Quebec since the 2013 Toronto floods," the company said.The UK & Ireland saw Storms Eleanor and Emma, with Emma known locally as the 'Beast from the East' and costing an estimated £47m pre-tax."We enter the second half of 2018 with confidence, while mindful of market challenges," said chief executive Stephen Hester."Good progress is being made in modernising technology platforms in every region. Underwriting actions and technical capability remain in focus. And we are pleased to have concluded an important new bancassurance alliance in Canada with Scotiabank, one of Canada's leading retail financial services providers."