This year, at least in Tennessee, the weather was very cold which leads to very low humidity. Two of my guitars went flat on me. My homemade cherry caster would not bow forward, even with the truss rod completely loose. And my Elan need a big adjustment (first time ever). The humidity returned and back to normal.
And as to .009 e strings - I switched to .010 and it is so much better in all aspects. Since you play bass, should not be a problem. I might move up to .011 one day. A friend of mine uses .013 and can bend like crazy.
Stephen