My least favorite runs are when it’s anything below about 20 degrees with a lot of wind. I’ve run countless times in single digits or even lower with wind and it’s miserable . Typically will draw the line if it’s zero or dangerous wind chill. My second least favorite is cold rain. I ran the HFD marathon one October in 44 degree rains the entire time and it was pretty much the coldest I have ever been . I was shivering for hours after . Sweating running, but cold rains.. soaked to the bone . I had to sit in the truck for like 30 minutes before I was able to drive safely