In the United States , warnings are issued by the National Weather Service to areas that will have winds within the range of 39 to 54 miles per hour or 63 to 69 km-h . In the United States , warnings are issued by the National Weather Service for marine areas experiencing , or about to experience , winds within the range of 39 to 54 miles per hour or 63 to 69 km-h ( approximately 34 to 48 knots ) .