And here's the full footage courtesy of YouTube:
Tomasz Schafermaker made the gesture at presenters Simon McCoy and Fiona Armstrong on the BBC News channel.
They said his forecast would be "100% accurate and provide all the detail you could possibly want".
The flustered weather presenter then realised he had been caught on camera and tried to cover up what he was doing by scratching his chin.
A BBC spokesman said: "Tomasz was not aware that he was on air, and whilst the gesture was only shown for a second, it was not acceptable.
"The News Channel presenter live in the studio acknowledged a mistake had been made, and we apologise for any offence caused."
The Polish-born weatherman began presenting on BBC Southeast Today in 2001 before joining the main BBC channels in 2006.
Wednesday, 18 August 2010
Weatherman Apologises For 'Giving The Finger'
The BBC has been forced to apologise to viewers after one its weathermen was caught giving the finger live on air: