You have to be early if you want plums this year. The cause is cold in flowering. It almost snowed when it was flowering. The bees were barely out, and we can see the result here.
Low temperatures and precipitation in the form of snow have been reported on several transitions during the day.
On Saturday night a new cold record was measured for July at Sognefjellshytta. There is unusually high cold and wind in several places in Norway right now. And little indicates improvement over the next few days.