Part of the fun of going to the top of Pikes Peak as a local is laughing at all the train riders who find out that on a 80 degree day, the top of the mountain is at 32 degrees or colder... and they’re in shorts and t-shirts.
My first time at RMNP it was mid 90’s in Denver. Low -mid 80’s in Estes. A friend of mine and I went for a hike up to Fern Lake. I had a day pack with, and she didn’t understand why. By the time we had gotten to the lake, the temp had dropped to 40, and I was pulling out fleeces and light gloves. (I had been in the mountains before, and always expect the worst.)