Here generally the worst time to burn a brush pile is in March and April, unless you are burning all the nearby grass at the same time . Grass is dry, humidity is low, and it is windy or will be in a day or two. Some parts of Kansas do not allow the burning of brush piles in April, just as an effort to reduce the amount of smoke that is being release during that time of year, since that is when all the native grass pastures get burned.