Taalas is the head of the Finnish Meteorological Institute and has a strong scientific background, with more than 50 publications on climate change and satellite methodologies.
He will replace the agency's veteran head, Frenchman Michel Jarraud, who is stepping down next year after three four-year terms.
"The importance of WMO and the national meteorological and hydrological services is growing due to a higher number of disasters hitting all parts of the world," Taalas said after his election.
"Proper early warning services are essential in protecting human life and property," said.
"Scientific know-how for climate adaptation and water resource management are also crucially needed in several WMO member countries."
Other contenders aspiring to lead the 191-nation Geneva-based body were from Russia, South Africa and India.
Taalas, who speaks a string of languages, including English, German and French, has been on WMO's executive panel since 2008, and is also a member of the Finnish Science Academy.
His election comes ahead of a key conference in Paris at the end of the year, marking the first attempt to clinch a world-wide deal on global warming since the near-disastrous 2009 UN summit in Copenhagen.
The Paris accord, which would take effect from 2020, would aim at limiting global warming to a maximum of two degrees Celsius over pre-industrial levels.