He was born in Dublin in 1944 but grew up in Waterville, County Kerry where his father was in charge of the Valentia Observatory.
During the 1970s he was a regular presenter of the daily weather forecast on Raidió Teilifís Éireann (RTÉ) television.
He was appointed as Director of Administration of the European Meteorological Satellite Organisation based in Germany in 1998 and retired in 2004.
Brendan McWilliams's daily "Weather Eye" column in The Irish Times, began in 1988 and became one of the most popular features of the newspaper.
For the last year of his life he made a weekly live contribution to Today with Pat Kenny on RTÉ Radio 1.