What is the average last frost date in Guelph?

According to the Government of Ontario the average last frost date in Guelph is May 11-17. (The average first frost date is October 1.) However, if you are gardening in Guelph’s surrounding areas such as Aberfoyle, Moffat or Rockwood your average last frost date is between May 17-24. (The average first frost date is September 26.)

Digging deeper, what these dates generally mean is there is a 50% chance there will be no frost in these areas after these dates, there is a 25% chance of a frost occurring 7 days after these dates and finally there is a 10% chance of frost occurring 14 days after these dates.

Guelph Area Typical Field Seeding or Planting Dates for:

Frost Hardy Crops: Approximately April 25 (Asparagus, Broccoli, Brussels Sprouts, Cabbage, Lettuce, Onions, Rhubarb, Peas, Spinach, Parsnips, Early Potatoes)

Semi-Frost Hardy Crops: Approximately May 5 (Beets, Carrots, Cauliflower, Celery, Late Potatoes, Early Sweet Corn)

Semi-Frost Tender Crops: Approximately May 25 (Snap Beans, Sweet Corn, Tomatoes)

Frost Tender Crops: Approximately June 5 (Cucumbers, Eggplant, Melons, Peppers, Squash, Watermelon)