Cool-season grasses are types of grass that thrive in the cooler temperatures of spring and fall. They grow best when temperatures are between 60°F and 75°F (15°C to 24°C). These grasses are commonly found in northern regions and are known for their lush green appearance during the cooler months. Examples of cool-season grasses include Kentucky bluegrass, fescue, and ryegrass. They are often used in lawns, parks, and sports fields because they establish quickly and provide a dense, durable turf. However, they may become dormant and turn brown during the hot summer months when temperatures rise above 80°F (27°C).