An American Canoe Association perspective...
Wind power or push is what builds waves and effects boat handling. A 10 knot winds force is doubled by a 14.2 knot wind and quadrupled by a 20 knot wind. In [specific area], an 18 knot wind usually means a Small Craft Advisory, other [areas] set their own, perhaps some higher.
Most intermediate touring paddlers paddle at about 3 knots, but if paddling into a 15 knot headwind, the speed made good drops to 2 knots and at 25 knots, drops to 1 knot made good or 1 nautical mile per hour. A routine 6 mile paddle home with little wind, would in theory take 2 hours, but with 25 knot head winds, an exhausting 6 hours of steady paddling.