Weather is only one factor, but it can really affect your travel plans, especially when you are planning a longer stay in Cromwell. The hottest months are usually July and August, with an average temperature of 22°C, while the coldest months are January and February, with an average of -1°C. The snowiest months in Cromwell are January, November, December and February, with each month seeing an average of 18 cm of snowfall.