BB,
Where are you living in Sac? Urban/Rural? I'm from the area too (Rocklin) Usually by now threat of frost would be close to being over, but as you have noticed, this year is special
(in a bad way) So I would say in 3 weeks should be pretty safe to plant it.
And bananas do not like Sacramento sun too much. It's HOT. Mine wilt like crazy during the day but spring back each night after I give them water. I would put it in an area of partial shade if you have it, but full sun should do just fine.
And I agree on the banana fuel.
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Average January Low: 40°F, Average August High: 95°F
Typical Low Each Winter: 28-30°F, Typical High Each Summer: 108-110°F, Annual Precipitation: 22 inches