I get contractions and a headache every single time the pressure gets low. With my last two pregnancies it was the worst the last 6 weeks. With my first, my water broke as a low pressure area was coming in. I asked at the hospital the last time I was there, and the nurse said she noticed that a lot of moms end up there when a storm is coming.
People say that it is a full moon, but I tend to think that our bodies are just more sensitive to the barometric pressure. I know that after my dd had surgery on her spinal cord, she would more readily get headaches when the pressure changed. I would collaborate with her, and we would get them at the same time, that was how I put two and two together.