Personal experience from three visits to Scotland from the USA in the past 7 years, all during last week in May and first week in June, and all on the coasts. First visit: Fife and up to Dornoch - cool but not cold weather, a little rain (and a little hail one day), only a little wind. Second vist: Ayrshire - mostly clear, only one or two windy days, and 60F to 70F. Third visit: Fife and East Lothian - a real mix of clear, calm, moderate days, very cold, very windy days, and very rainy but not-too-cold days. Advice: prepare for anything and everything.