I filmed this last week near the town of Chehalis, along the Newaukum River, in Southwest Washington State. The waters receded temporarily, but are rising again now that heavy rains have returned.
You can opt to just not update it.
The PIC is required to keep the drone in a safe operating condition. There is no legal requirement to keep firmware up to date, but you should.
However, if it's a major update, it's best to wait a few days...