Winters are not cold there, if that is what you were talking about. If instead you were talking about the cool summers, apparently those aren't a problem for this plant either.

ZONE 17: Marine effects in Southern Oregon, Northern and Central California

The
climate in this zone features mild,wet, almost frostless winters and
cool summers with frequent fog or wind. On most days and in most places,
the fog tends to come in high and fast, creating a cooling and
humidifying blanket between the sun and the earth, reducing the
intensity of the light and sunshine. Some heat-loving plants (citrus,
hibiscus, gardenia) don’t get enough heat to fruit or flower reliably.
In a 20-year period, the lowest winter temperatures in Zone 17 ranged
from 36 to 23°F (2 to –5°C). The lowest temperatures on record range
from 30 to 20°F (–1 to –7°C).Of further interest in this heat-starved
climate are the highs of summer, normally in the 60 to 75°F (16 to 24°C)
range. The average highest temperature in Zone 17 is only 97°F (36°C).
In all the other adjacent climate zones, average highest temperatures
are in the 104 to 116°F (40 to 47°C) range.

http://www.sunset.com/garden/climate-zones/sunset-climate-zone-northern-california

Sunset 17 extends all the way up to Gold Beach.

This is Kahili or Hawaiian ginger and it grows very well here in Brookings.

https://www.facebook.com/285589928135801/photos/pb.285589928135801.-2207520000.1473530286./285625718132222/?type=3&theater

Winter before last was mild here, this past Winter was much colder and I lost things that were untouched the year before. This stand of Kahili is 1/2 block from the water, I'm 3 blocks from the water. It would be somewhat protected by the overhanging trees, just in that one spot in the morning sun, but may be picking up needed reflected heat from the street right in front of it. It canbe highly variable here with Brookings and farther nortH to Pistol River being more Banana belt than we are......

>Brookings and farther nortH to Pistol River being more Banana belt<

Yes I know about that. Nevertheless the overall conditions there are still Californian. You didn't indicate what it was about the ginger being there that was such a surprise to you personally. The town's general aspect could easily lead some to think Crescent City was as cold as points much farther north.

Not that we don't grow some ginger lilies up here also. I have 'Tara' in bloom at the moment myself.

Crescent City is colder than Brookings and Pistol River...Winter and Summer...my experiences with Gingers have been in SoCal Sub-tropical zones, but even there I got the best results from positioning for heat, the best large stand ever being with some that I gave to a friend who planted them beneath avocados right beside the road, getting a lot of reflected heat from the asphalt. This turned into a huge patch of H. coronrarium. I had thought that Crescent City would be..

Too cold in winter, having had snow a few winters ago right on the beach

Not warm enough in Summer due to our very many overcast and foggy days.

You can leave Brookings at 85 degrees and come home to 70 degrees here....which we usually find welcomimg...