This spring’s weather has been ideal for some long weekend guests, unwanted guests – black flies.

Black flies can put a damper on a long weekend. Already the little bugs have been spotted north and experts say to expect them to be around for the long weekend.

Black flies tend to lay their eggs near fast moving streams. They become more active once temperatures get to be around eight or ten degree Celsius. But the weather needs to get really hot for the flies to die off and that doesn’t look like it will be happening anytime soon.

“The bad news is May is not going to be that warm. Usually the black flies are bad for a week, the weather gets warm, kills them off. But May is going to be cool. We’re going to get cool weather so we’re going to get an extended period of black flies this spring,” says naturalist Bob Bowles.

Experts say in order for the flies to disappear you need about four or five consecutive days of warm weather at least 15 degrees Celsius.