My tomato plants are huge. I have plenty of blossoms but none are setting any fruit. Is this due to an unusally mild May? Can I do anything to help them set fruit such as trying to pollinate them myself and if so, how do I do that?

If your location is where it is really warm, such as California or Florida then your problem is that the Nitrogen of the soil is in the Nitrate form which causes foliage growth but not fruit. To fix the problem add 1 quart of apple cidar vinager to 5 gallons of water and then water each plant with a quart of this
and you will get fruit set.

If you live in the cold climate zones ( Midwest etc.) this is too
early for fruit set and everything is normal. They will produce fruit over the summer months.