However , the summers are short ; no more than three months of the year ( but at least one month ) and must have a 24-hour average temperature of at least 10 Â C ( 50 Â F ) to fall into this category of climate . However , the summers are short ; no more than three months of the year ( but at least one month ) must have a 24-hour average temperature of at least to fall into this category of climate .