Never had this problem before

Tonight I was excited to print the third color of my streetscape print and I immediately ran into a problem. The third layer wasn't lining up with the two layers underneath. Yikes! It was 2-3mm too short, which doesn't sound like a lot, but is easily seen by the eye of the viewer. It threw me for a complete loop. Frustrated and perplexed, I started troubleshooting. What was I doing wrong? I even had a test print from last weekend that showed the third layer printing just fine.

Then it dawned on me. We've had very heavy rain all week, which increased the humidity drastically and stretched the paper. The stretching of the paper probably threw the registration of the layers out of wack. A quick Google search for an answer confirmed my hunch. So I put the brakes on tonight's print run after losing the first four prints. I'll wait until the rain abates and hope the paper shrinks back again to the approximate same size. Or am I missing something else?

Fingers crossed.