If you’re hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Littleton: The hottest months are usually July and August, with an average temperature of 21°C, while the coldest months are February and January, with an average of 0°C. The snowiest months in Littleton are March, February, October and December, with each month seeing an average of 27 cm of snowfall.