This is an interesting question! According to a naturalist for Vermont State Parks who answered this question online a couple of weeks ago:

“Our white pine trees--taller than every other tree in the Vermont woods, are heavily laden with cones this year. These giants of the forest started the summer months growing bright green female cones in large clumps at the ends of all the upper branches. The cones were so plentiful, they weighed the branches into curved arches pointing down. Throughout the summer, the seeds hidden under the cone bracts developed, the cones turned brown, and the seeds came sailing out with their adapted wing--hopefully planting some new white pines. At least that is the goal of the pine tree as it grows more and more cones, and more and more seeds.

The summer of 2016 we saw a drought. Remember how low the lake levels dropped that summer? Well, our trees are reacting to that stress by producing way more seeds, nuts and fruits than normal. Our pine trees started developing this year’s cones in 2016, so the drought triggered them to grow more. The weather in the summer of 2017 was adequate for pines to fully develop all these cones into seed bearing vessels.

We see this happening with more trees than the white pines. Maybe you’ve noticed more acorns than normal, extra samaras from maple trees winging around, tons of spiky beech seeds all over the ground, or you picked extra apples at the orchard last month. This natural reaction of our trees to weather patterns reminds us that there are so many factors influencing the happenings in nature.”

In addition, I found this interesting answer to the same question from Peter del Tredici, who is Senior Research Scientist at the Arnold Arboretum in Boston:

Pine trees don’t produce the same amount of cones each year, he says, to throw off the insects that eat the cones. Trees do this as a way of avoiding these predators, because if they produce the cones on erratic, unpredictable cycles the insects can’t adjust to them.” 

Hope this is helpful.