The highest level of waterproof jacket typically refers to those with the highest waterproof rating. These jackets are often rated as "waterproof" or "waterproof and breathable" and are designed to withstand heavy rain and snow for extended periods while still allowing moisture from sweat to escape.
They usually have fully taped seams, waterproof zippers, and durable water-repellent (DWR) coatings to ensure maximum protection against moisture. Some popular waterproof ratings include Gore-Tex ePE and Columbia's OutDry Extreme. These jackets are ideal for extreme weather conditions and outdoor activities like mountaineering, skiing, and hiking in harsh environments.