I can usually assess the temperature close enough by feel and experience, within a couple degrees. Thats in humid SE conditions, sheltered from wind, and inactive.
Put me out west where its dry , start moving and heating up, and Id be way off. Howver the only thing Im ever interested in was the overnight low, and that, Im pretty good at.
SUN has several small thermometers. Although graduated in 5F increments, the ones I have have proven fairly accurate (used on my kids science project, and compared with a better thermometer).