Brush piles are problematic and can cause many wildfires. This is because they often burn for long periods of time, during which extreme conditions may develop.
Remember that embers can travel great distances from brush piles and create spot fires. The best time to burn a brush pile is when vegetation is actively growing and thus has a high moisture content. Under these conditions, spot fires are less likely to occur. If this is not possible, then fuel needs to be eliminated around the brush pile through mowing, grazing, prescribed fire, etc.