Because you never know when it will rain or wind to disturb your wedding It should be planned in an appropriate season when there is no snow, rain or freeze due to snow? Also think of furniture. Instead use flowers that will last for long time. Do not use delicate items or flowers. Too many flowers and flowy things may ruin your celebration. You need to do more. If your wedding is in day time, you might have darkness.
If your wedding decorations. Light is also an important issue when you consider outdoor wedding decorations. Make small lake or fountain to add more nature to the decoration. But if you still want an outdoor wedding decorations. The best rule for outdoor wedding decorations. While thinking of a park wedding make sure that the area is not too small or big for your guest list. The soothing breeze, greenery, the moonlight and sparkling stars would be already adding beauty to the venue. Make small lake or fountain to add more nature to the venue.
Because you never know when it will rain or wind to disturb your wedding decorations. Would you like to see your guests are all soaked in due to snow?