Usage of ように in 「短い秋」

Hi. I’m probably (definitely) getting ahead of myself but in the phrase, “夏 の ように 暑く”, I’m looking up ように in JMdict and I see two versions: 様に and 陽に, and I think here we mean the latter, 陽に. Is this right? Any clarification would be most useful. Thank you!

I don’t know why you thought it should be 陽に but I think 様に is the right one in this context.

-の 様に is a very widely used expression meaning “like”, “as”, or “similar to”. 様 means appearance, form, or method.
陽に seems more rare and should be “openly”, “in the open”, “without hiding”. 陽 is sunlight (太陽 = sun).

So “夏 の ように 暑く” is “warm like summer”.

The whole sentence “少し 前 まで 、夏 の ように 暑く 、半袖 で 過ごして いた のに 、あっという間 に 冬 に なって しまい ました” may be translated as “Even though just a short while ago it was warm like summer and we were getting by wearing short sleeves, it has turned into winter in the blink of time”.

There is nothing left to add, and nothing to take away.

Thank you so much for your patient and thorough answer, much better than I had any right to expect! I was (very foolishly) looking up the words in the dictionary and only later learned, as you wrote, that のように is the phrase I should have been looking up.