Strange Ending

Today was actually almost perfect weather for running. The temperature was right at freezing, the sun was shining, and the breeze was almost non-existent. Donning long sleeves, mittens, and a stocking cap, I ran about 5.8 miles with no issues. As I ran up the big hill before entering the neighborhood I suddenly felt like I was going to throw up. I coughed and retched a couple of times as I walked and then turned the corner. Three more times I was prepared to vomit in the side yard of the lucky person with the first house in the development. I started feeling overheated and took off my cap, and as soon as I did the feeling vanished. The only thing I can figure is that I was overheated even though I didn't really feel like it. After another half block of walking I finished up the run at 6 miles. The weirdness hasn't returned since then. Strange, but something to remember next time I layer up for a run in the cold.