Geminids maximum is expected to occur on December 14th, 06h30m UT, with ZHR = 120 hr-1 at peak. 
Since the peak has shown slight signs of variability in its rates and timing in recent years, please note that the more reliably-observed maxima during the past two decades have all occurred within the range ?sol = 261.5 and 262.4 degs, 
equivalent to 2017 December 13th, 14h UT to December 14th, 11h UT. 
Near-peak rates usually persist for almost a day, while fainter meteors should be most abundant almost a day ahead of the visual maximum. 
The Geminids peak is typically quite broad (thus ensuring a several-days-long period of good MS activity), although the rates sometimes decay fairly quickly after the maximum.