In extreme conditions salt on the rotorblades may have significant effect on performance. In one instance a rescue helicopter with a cruise speed of 110 kts could only be flown at 80 kts due to vibrations. This happened following hoist operations in a 80kts wind. In another case a helicopter in the North Sea was forced to reduce speed to the point where it was doubtful i would reach land. However, after flying through rain, inter-helmet temperture returned to normal.