Most fires related to ash removal start this very way because a lidless pail sits exposed when a winter's breeze comes along, and stirs the pail's contents. The coals become active again, the pail's temperature increases, and the floor can begin to char. Worse yet, the winter's breeze actually disperses the now-active coals onto the wood porch and worse problems soon begin. If the ashes are from wood, they make an excellent addition for gardens because they are high in potassium, calcium, sodium, magnesium, and phosphorus. In areas where there is high rainfall, the soils there are typically high in acid.
Wood ash can actually help decrease that acid level.
Dry areas, however, tend to be more alkaline in nature. Wood ash in dry areas can exacerbate that problem. Since regions will vary, it's best to have your soil tested through a local extension agent or garden center to see if wood ash can be helpful to your soil prior to applying. If the ashes are from burning coal, then you must be more aware of proper removal for many reasons. First, you will have much more ash to remove versus wood.