When do the flies begin feeding?

[NJChileHead]

Hi Folks,

We're planning an outing in late May, and after making the arrangement, I may have neglected to consider one factor-do people usually start seeing (feeling) the biting flies by then?

 

[dogg57]

They will be feeding.With this crazy weather who knows. I go out now ready for them.(Deer flies)
http://bugguide.net/node/view/117/data

 

[46er]

Hi Folks,

We're planning an outing in late May, and after making the arrangement, I may have neglected to consider one factor-do people usually start seeing (feeling) the biting flies by then?

Which ones; the deer flies or the greenheads. Greenies need a lot warmer temps.