too late with wintergrass?

hi everyone

with the warmer temps winter grass has just shot up all over the place on my front lawn.. reading around on google it has suggested that May is the time to use chemicals to kill these and during warmer months the weed is too strong and will out grow any chemicals sprayed..

is this true? if so, should i simply wait until May before covering the front lawn with this stuff? (Wintergrass killer)

THanks.