Halton region Master Gardeners

Come Grow With Us!

, ,

Canada’s Plant Hardiness Zones Update for 2025: What Gardeners Need to Know

Canada’s Plant Hardiness Zones have been updated for the first time in over a decade! Based on 1991–2020 climate data, most of the country has shifted up by ½ to 2 zones due to warmer winters, longer frost-free periods, and hotter summers. Want to know your new zone? Check out the full article attached here.

Cathy Kavassalis – Halton Master Gardener

August 30, 2025

Canada’s Plant Hardiness Zones Updated

Natural Resources Canada has released the first update to Canada’s Plant Hardiness Zone Maps in over a decade, based on 1991–2020 climate data.

Key Facts

  • Canada’s system is different from the USDA’s.
    • It uses 7 climate variables (see below) and not just minimum winter temperature
      • minimum winter temperatures,
      • length of the frost-free period,
      • summer rainfall,
      • maximum temperatures,
      • snow cover,
      • January rainfall
      • maximum wind speed.

These seven together generate a suitability index that’s then divided into hardiness zones (0 to 9, with “a” and “b” subzones).

  • Since 1961–1990, most of Canada has warmed by ½ to 2 full zones.
  • 99.6% of changes were increases, though a few small areas (e.g., parts of Newfoundland, Vancouver Island, Prairies, and northern Quebec) saw decreases.

The biggest drivers of change were:

  • warmer winters
  • longer frost-free periods
  • hotter summers.

Ontario Highlights

  • The GTA (Greater Toronto Area) is Zone 7a.
  • Ottawa has changed only slightly and remains 5a.
  • Saute St. Marie is Zone 5a.
  • Windsor is Zone 7b.

👉 Check your nearest municipality here

The Canadian plant hardiness zone map for the 1991-2020 climate period, with insets showing greater detail for: (a) southwestern British Columbia, (b) southern Ontario, and (c) the Maritime provinces of Nova Scotia, New Brunswick, and Prince Edward Island.

Gardening Implications

Warmer temperatures and longer seasons may allow for extended harvests and for growing a greater variety of fruits and vegetables, but drought, heavy rains, and false springs mean gardeners will face increasingly unpredictable conditions.

Invasive Species and Caution

  • Be aware that invasive plants, pests and diseases will have new opportunities to spread.
  • Use caution when adding new plants, soils, or mulches to your garden.
  • Always check a plant’s invasive potential before choosing new introductions (type the botanical name + “invasive” into your search engine).
  • Be careful not to move invasive species between areas (movement of plants, wood, soils/mulches, and indirectly on boots & vehicles).

👉 Learn more here

Comparing to US Grow Zones:

Here is a map that looks at the lowest extreme temperature. This allows us in Canada, to compare our gardens to to those located in the United States.

View More Here About the US and Canadian Zones

Further Reading

All Images:

Trending