Six varieties of wheat and triticale (DDK1029, TL2934, PBW 174, DPW 621-50, PBW 343 and PBW 590) were sown in the field of Indian Institute of W heat and Barley Research, Karnal, Haryana (IIW BR) and Regional Research Station, Dhaulakuan under Himachal Pradesh Krishi Vishvavidyalaya, H.P during seasons 2012-13 and 2013-14 to study the role of environmental factors on the development of powdery mildew of wheat (Erysiphe graminis f.sp. tritici). The disease development was positively correlated with temperatures and negatively correlated with evening relative humidity and rainfall under field conditions. Best fit regression model was developed with maximum temperature, evening relative humidity and rainfall across the varieties and locations which explains 64% variation in powdery mildew disease.