If you must pile the grain outside on the ground, drainage is crucial. The pile should be on high ground and the earth crowned under the pile. Place plastic (6 mil) on the ground to keep ground moisture from wetting the grain.

Plastic or tarp covering the pile will reduce wetting by rain and snow and minimize damage by wind and birds. The top surface should be smooth to aid in drainage. The cover should carry the water away from the piled grain to prevent wetting the grain. Condensation under the plastic may cause problems unless it is controlled with aeration. Move airflow under the plastic to carry the moisture away. Drainage tile under the plastic has been used as an air intake duct when the aeration fan exhausts air from the bottom of the pile. The ability to cool the grain by aeration improves the storability of the grain. Run the pile north and south to allow the sun to dry off the sloping sides.
Erect a fence to keep animals off the pile. Nearby trees aid wind protection but can also be a home for birds and might result in snow drifting on the pile.