Kudos for taking on this experiment.

That said, I've been in places where it was too cold for any whistle to function properly, pea or no pea. Once it gets into the sub-zero temps (say, -15F/-26C) all bets are off.

For me, it was the thought of cold metal sticking to exposed lips that made me switch to a plastic Fox 40 -- not the possibility of an immobile pea.

From an article entitled, "5 Worst Weather Super Bowls":

...Referee Norm Schachter had a metal whistle freeze to his lips. When he tried to rip it free, it took the skin off his lip, leaving a frozen, bloody lip! Referees then had to simply yell out commands instead of blowing the whistle to end plays.

1967 NFL Championship "The Ice Bowl"
Dec. 31, 1967 (Green Bay, WI)

http://www.weather.com/outlook/weather-n...12-02-02?page=6