Allegedly there is a confirmed case of late blight in tomatoes as far north as Northern Kentucky (Boone County) (part of the greater Cincinnati area). Late Blight normally freezes out over the winter in the northern states so it's usually not a problem in the northern states until the spores work their way north which is usually later in the year. The ground is already wet and there is a forecast or more rain and some cool days; which regretfully would be idealistic conditions for late blight to flourish.
Sometimes late blight can get a jumpstart in the northern states when precautions are not followed. Sometimes contaminated
seeds or
potatoes can reintroduce the late blight. I would imagine that the late blight could survive the winter in the shelter of a
greenhouse.
Last year there seem to be some particularly aggressive strains of late blight; in combination with an unusually wet and cool summer in many areas which allowed the late blight to decimate many crops like tomatoes.
