The climate in Hamilton is relatively moderate compared to the other cities in Canada. It is characterized by humidity that makes summer temperatures feel hotter than they are.
Summers: The average temperature in July is approximately 22 degree Celsius with very high humidity that can aggravate the discomfort and smog conditions. This is also a high season for tourists.
Winters: The average temperature during peak winter is about -5 degree Celsius. The winter snowfall greatly varies but on an average stays in the range of 50 inches. Months of December to March are the winter months that are perhaps the coldest with temperature variations observed between lower city and escarpment area. This is basically off-season in Hamilton.
Spring: Spring months in Hamilton are between April to June when the weather is pleasant for all the outdoor activities. The fall months of September and October are pleasant too.
So, the best time to visit Hamilton is during spring, in the months of April to June.