Heatwaves have shown increasing trends in intensity, frequency, and duration, with these trends expected to worsen due to enhanced global warming. This study, using the Berkeley Earth temperature dataset and key heatwave metrics, systematically examines regional and global observed heatwave trends. The results indicate that heatwave frequency demonstrates the most rapid and significant change in almost all regions, with cumulative heat showing significant increases since the 1950s. Trends in heatwave frequency, duration, and cumulative heat have accelerated since the 1950s, but climate variability can influence these trends over multiple decades. The study provides a comprehensive assessment of regional observed heatwave trends, highlighting the need for a period of at least 3-4 decades to robustly assess changes in heatwaves. The findings have important implications for understanding and managing the impacts of heatwaves on various systems, including human health, agriculture, and public infrastructure.Heatwaves have shown increasing trends in intensity, frequency, and duration, with these trends expected to worsen due to enhanced global warming. This study, using the Berkeley Earth temperature dataset and key heatwave metrics, systematically examines regional and global observed heatwave trends. The results indicate that heatwave frequency demonstrates the most rapid and significant change in almost all regions, with cumulative heat showing significant increases since the 1950s. Trends in heatwave frequency, duration, and cumulative heat have accelerated since the 1950s, but climate variability can influence these trends over multiple decades. The study provides a comprehensive assessment of regional observed heatwave trends, highlighting the need for a period of at least 3-4 decades to robustly assess changes in heatwaves. The findings have important implications for understanding and managing the impacts of heatwaves on various systems, including human health, agriculture, and public infrastructure.