Ontario · Growing Zone 5b
Gardeners in Ottawa, ON can expect the average last spring frost around May 7, and the first fall frost around October 12, based on historical Environment Canada frost data for the area. That gives Ottawa a frost-free growing season of roughly 158 days. Actual frost dates shift by a week or two year to year, so use this as a planning baseline rather than an exact guarantee, and always check your local forecast before moving tender plants outside.
Most warm-season crops (tomatoes, peppers, squash) need transplanting only after the last frost has passed, and are usually started indoors 6 to 8 weeks before that date. Cold-hardy crops (peas, lettuce, spinach) can often go in the ground a few weeks before the last frost. As Ottawa's first fall frost approaches in October, it's time to plan the last harvests for anything frost-sensitive still in the ground.
GrowBlock builds your whole season timeline around dates like these automatically, indoor seed starting, transplant windows, and harvest, tuned to Ottawa specifically.
Plan your Ottawa gardenAround May 7 on average, though it can vary by a week or two either way depending on the year.
Ottawa is in zone 5b, with a frost-free season of about 158 days.