It can get down to 27F in the winter where I'm located, but the last time it was that cold was about 10 years ago. Normally, we see between 29-32F as the lows at night. However, these lows typically only last for a few hours at night, and it always warms up beyond freezing during the day. What's even more damaging is prolonged cold, wet days/nights. Last year, we had light frost for maybe 1-2 days, and that didn't cause any leaf damage. It was the days were it was in the 40's at night and high 50's during the day for weeks on end with lots of rain that really damaged the plants.
In contrast, we had a lot of cool, dry days this december, and temps. were about identical to last year. Zero of the bananas showed cold damage to the leaves until it started raining hard in January. Rajapuri is definitely slightly more cold tolerant compared to american goldfinger fHIA-1. Ice Cream also has a high level of cold tolerance compared to other cold tolerant varieties.
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Here's the complete report of "not namwah" which turned out to be raja puri (ID is with 100% certainty):
rajapuri outdoors in Northern California (grow report)