How Cold is Too Cold for Outdoor Recess?

How cold is too cold for recess? Maine schools and can't seem to agree.

According to the Bangor Daily News, Lauren Jacobs of the University of Maine surveyed Maine schools about their outdoor recess policies and temperature thresholds.

Jacobs discovered that most northern schools didn't cancel outdoor recess until the temperature was below zero and coastal schools canceled outdoor recess as high as 20 degrees. Through her studies, ultimately Jacobs felt that Maine doesn't have extreme enough weather to justify having indoor recess.

What do you think? Should there be a set temperature, if one at all, to cancel outdoor recess?