From the ”上級で学ぶ日本語” N2 level book, page 51, ローソク島 reading, 2nd to the last line of the 2nd paragraph.
In the story the author is convinced to go visit "Candlestick Island" by the employees and staff of the hotel he's staying at. Apparently when the sun sets at night it can make it look like the candlestick of the "candlestick island" is being lit. Everyone is kind but the weather turns cloudy and they're not sure if they'll be able to see it.
It is here that the author wanting to express his gratitude to the staff for trying so hard thinks or is about to say:
I was inititially confused because I mostly know 相手 as meaning companion, partner, company or opponent.
So "Even though (you/the staff) were companions of nature....(we won't be able to see the sun set on the island)" was my intial brain translation but that didn't make much sense. Asked the sensei, and I got the meaning of the phrase but I still have no idea how we got there from these specific words.
The author is apparently wanting to express gratitude to the staff for trying so hard despite the weather/nature being what it is.
I did some digging and 「相手にする」has a less commonly used meaning that can mean "to deal with" and my Japanese friend confirmed that another way of saying it would be 「自然を相手にしているのに」is another way of saying what he's trying to convey which makes a lot more sense.
But just because I know what it means, doesn't mean I have any understanding of how the original phrase actually means that.
How exactly is「相手のこと」being used here? Is 相手 being used as a する verb with the する ommited? What does it mean? How did I get here? Am I having a stroke?