Hiscox said the devastation wreaked by Hurricane Harvey on the United States will cost the insurer $150 million (£110 million) in claims.
The FTSE 250 firm said the estimate was within the modelled range for a disaster of that scale and was based on an insured market loss of $25 billion (£18 billion).
It came as the company warned that "natural catastrophes" would run up a big bill for the insurance industry this year, but assured that the sector would be able to cope.
Alongside the aftermath of Hurricane Harvey, America is also grappling with the impact of Hurricane Irma, which made a devastating sweep through the Caribbean before slamming into Florida.
Chief executive Bronek Masojada said the reinsurance protections for the group were substantially intact.
He added: "Insurance exists to help individuals and companies recover from the devastation caused by events like this, and our priority is to pay claims quickly so that they can do that.
"At the same time, Harvey has also highlighted the lack of flood cover for large parts of the US market.
"2017 will be an expensive year for natural catastrophes but the industry can cope."
Hiscox, which provides cover for around 60,000 homes in the UK, said it would also provide an estimate for the cost of Hurricane Irma once the impact of the event was fully understood.
He added: "Insurance remains a cyclical business and after a long period of price reductions, insurance rates in the affected areas and in specific sectors such as large property are likely to increase.
"In the wider global insurance market for large risks, we expect rates to stabilise and begin to increase."
The insurer saw half-year profits rise 12.5% when it announced its results in July, helped by a solid performance in its retail business.
The company revealed that pre-tax profits, stripping out the impact of foreign exchange, climbed to £133.5 million in the six months to June 30, up from £118.7 million a year earlier.
However, it was a much gloomier picture when taking foreign exchange movements into account, with profits halving to £103 million over the period.