Understanding how electricity demand responds to the ambient temperature is critical for the safe andefficient operation of the power system. Examining an extended series of daily electricity records from2011 to 2020, we find that there is a significant nonlinear temperature-electricity load response approximatinga cubic function of the temperature or the cooling degree days in the two major power subsystemsin northern and southern Vietnam. Such a nonlinearity indicates a major concern for power supplyinfrastructure to meet increasingly more severe weather-induced load variations. We conclude the paperwith several critical recommendations for future power development policies in Vietnam.