When I moved to Shetland in 1980 May was the foggy month including one year when my mother was here for 5 days and had fog the whole time. In recent years it appears that the fog has moved to June and July.
Oh, but I do love fog when we are at our house on the coast of Maine, BUT not for a month. We went to a Canadian Island, Grand Manan off the coast of Maine for a few days once. It was so foggy we couldn't see the lighthouse and jumped when the foghorn blasted!