And there really is strain. When the wind is howling, you can see the lines stretch.
Sizing of the docklines is important. This is a case where too strong is not such a good thing. Ours are 5/8" nylon. With our weight, there is a fair bit of stretch in the lines when the boat surges. This stretch removes the shock loading on the cleats, and is a good thing. If we went to heavier line, we would lose this shock absorbing quality.
Here is a plot of wind speed (in knots - multiply by 1.15 to get mph) from the past couple of days.. yes, there was gust to 38 kt on the 5th, and on the 7th, a lot of time was spent steadily blowing between 25 and 30 kt. (By the way, gale force wind begins officially 35 kt.) This plot comes from a weather station that we can see from right here in the marina - it is pretty reflective of conditions here at the dock.
This is definitely NOT the gentle patter of rain on the deck I blogged about earlier...