Planning for the weather is a good way to make your trip to Mill Creek relaxing and enjoyable, especially when you're splurging. The hottest months are usually July and August, with an average temperature of 18°C, while the coldest months are December and January, with an average of 0°C. The snowiest months in Mill Creek are March, January, February and April, with each month seeing an average of 90 cm of snowfall.