Heatwaves, characterized by prolonged high temperatures, have become a recurrent and severe phenomenon in Bangladesh, posing significant risks to public health, agriculture, and socioeconomic stability. This study analyzed the characterization and long-term projections of heatwave patterns in Bangladesh's western and northwestern climatic zones, addressing a critical gap in understanding regional vulnerabilities to extreme temperature events. Heatwave thresholds were defined using the Bangladesh Meteorological Department Criterion, a percentile-based criterion, and the Indian Meteorological Department Criterion, providing a comprehensive framework for assessing heatwave intensity and frequency. Using nine bias-corrected general circulation models from CMIP6 (Coupled Model Intercomparison Project Phase 6), the study examined historical heatwave patterns (1990-2014) across five cities, Bogra, Chuadanga, Dinajpur, Ishwardi, and Rajshahi, and evaluated future projections for three epochs: Epoch