Shame some of the comments are being deleted so quickly, as there's clearly a large gap in knowledge here. Maybe a gap I could've addressed today: flying with a reasonably high aspect & thus critical wing in -5 or so. Or maybe a few weeks ago, across the Irish Sea at FL105 on a lovely winter's morning with an OAT of -18? Both utterly clear of ice on the wings or the engine intake, and with a piston engine cleared down to fuel temps of -30 on Jet A-1. Or a couple of times getting through cumulus clouds at rather higher OATs with anti-icing systems switched on to control the buildup of ice and allow me to get to clearer air - in a twin rather than a single, fortunately.
Icing conditions are not purely defined by temperature - it does take a certain amount of humidity to actually create the ice.