The climatological distribution of heat and cold waves of two important agro-climatic zones zone-I (North Alluvial Plain), zone-II (North East Alluvial Plain) of the middle Indo-Gangetic Basin of Bihar state of India was analyzed. We used series of daily maximum and minimum temperature data from 1969-2015 of five stations. Results reveal that zone-I and zone-II experienced 248/184 and 275/199 average number of heat and cold events, respectively. The trend analysis exhibited almost similar results for both the zones. The zone-I experienced on an average 4.22 and 7.22 heat and cold wave days per season (hot & cold weather period), respectively. There was a non-significant increasing trend @ +0.04/ year for heat waves and significant decreasing trend for cold waves (-0.13/year). Zone-II on an average experienced 3 and 12 HW and CW events per season (hot and cold weather period), respectively. In this zone, heat waves were found to be increasing @ +0.11/year, whereas, significant decreasing trend was found for cold waves (+0.32/year). Study also revealed that, heat waves were more frequent and longer in June and May in zone-I and zone-II, respectively. Whereas, cold waves were more frequent and longer in January for both the zones. These extreme events have profound impact on wheat crop if coincides with its critical stages. However, shifting planting dates and adoption of heat tolerant varieties may help in minimizing the negative impact of these extreme events.