Resources · Climate

Hardiness Zone in County of Forty Mile

County of Forty Mile is generally treated as Canadian plant hardiness zone 4a, with a frost-free window on the order of 125 days. The zone is read from the Natural Resources Canada plant hardiness map (4th edition, 1991–2020 normals) at a representative quarter; frost dates are a regional table keyed by zone, not a logger on your fence. Those two numbers decide more tree deaths than soil tests do.

Zone 4a with about 128 frost-free days. Heat and drought are the limits; frost rarely is.

What the zone is — and is not

Agriculture and Agri-Food Canada’s plant hardiness maps combine several climate variables, not just one winter low. A zone 4a label means a typical winter in this belt, not the worst winter of the decade, and not the frost pocket at the bottom of your driveway.

Use it to:

• Filter nursery stock (do not buy zone 5 peaches for a County of Forty Mile field)
• Plan shelterbelts that will still be standing in twenty years
• Time cover crops against a 125-day window

Do not use it to:

• Ignore a north-facing draw
• Skip a thermometer logger for one season
• Assume the town of Medicine Hat and a rural quarter share the same last frost

Frost-free days in practice

125 days is a regional sketch. Last spring frost and first fall frost move with elevation, wet ground, and cold-air drainage. In County of Forty Mile, watch:

• River and lake edges that radiate heat at night — or collect cold
• Open peat or muskeg that frosts early
• South walls and gravel pads that buy you a week

A food forest that needs 130 days will fight this county most years. A shelterbelt of zone 4a natives will not.

Pair climate with water and sun

Zone is only one pillar. A 4a site with a 100 m well and 1.2 kWh/m²/day in winter is a different homestead than the same zone on a municipal line. Plan trees, wells, and panels on the same map.

Flood or wet ground near South Saskatchewan River valley, Milk River valley, Pakowki Lake lowlands can also shorten the effective season by keeping soils cold in May.

See this for your specific parcel

Generate a free land report for a property in County of Forty Mile →

Sampled data for County of Forty Mile

From a Land Intelligence report run on a representative quarter in Township 7, Range 10, W4. These are measured or record-based values for that location, shown to put the county figures above in context. They are not your parcel.

Growing zones near County of Forty Mile: Taber (zone 4a) · Medicine Hat (zone 4b) · Alberta growing zones map

Neighbouring counties: MD of Taber (65 km) · Cypress County (73 km) · County of Warner (88 km) · Lethbridge County (109 km) · Compare County of Forty Mile with another county

Sampled from the live report pipeline at a representative quarter in Township 7, Range 10, W4 on 2026-10-08: well depth, hardiness zone, solar irradiance (31 well records within 5 km). Text reviewed 2026-10-09. Methodology.

Common questions

What should I plant in County of Forty Mile?

Start with zone 4a stock and a 125-day season. Then walk frost pockets.

Is the town of Medicine Hat the same zone?

Often close, not identical. Elevation and cold-air drainage on a rural lot can run colder than town.