Weather is only one factor, but it can really affect your travel plans, especially if you're planning an extended stay in Harkness. The hottest months are usually July and August, with an average temperature of 18°C, while the coldest months are January and February, with an average of -4°C. The snowiest months in Harkness are January, February, March and November, with each month seeing an average of 19 cm of snowfall.