average temperature in honolulu august
1 There is a range/ variation of diurnal average temperatures of 8 C (14.4 F). 2  August is the hottest month (hot) having an average temperature of 27.4 degrees Celsius (81.32 degrees Fahrenheit). 3  January is the coldest month (really warm) with an average temperature of 22.7 degrees Celsius (72.86 degrees Fahrenheit). The mean temperature in Honolulu, Oahu, Hawaii is fairly hot at 25.1 degrees Celsius (77.2 degrees Fahrenheit).