National Flannel Day is observed worldwide on February 10 each year, celebrating the comfort and warmth associated with flannel fabric. This unofficial holiday encourages people to wear their favorite flannel shirts or cozy flannel pajamas. Flannel, a soft fabric that can be made from wool, cotton, or synthetic fibers, has origins dating back to 16th-century Wales, where it was initially known as “Welsh cotton.” Over the centuries, flannel has evolved in its associations, from being popular in sports like cricket to becoming a staple in the grunge music scene of the 1990s. Today, flannel is commonly recognized for its plaid patterns, although not all flannel shirts are plaid. Celebrations can include wearing flannel, sharing photos on social media with hashtags like #NationalFlannelDay, and learning about the fabric's history.