Using the right mowing techniques, you can improve the health of your lawn and prevent burnt-looking spots that appear after mowing. One common cause of burnt spots in lawns is dull lawn mower blades. If the blades of grass in your lawn look jagged and torn after mowing, it is time to sharpen your mower blades. Mowing during the hottest times of day can also cause your lawn to turn brown. We recommend mowing later in the afternoon or early evening.