EN · FR
☰✕
Ontario · climate station 6127514 · 180.6 m

Sarnia Airport

Average last spring frostApril 29
Average first fall frostOctober 19
Frost-free period172 days

1981–2010 normals; ECCC quality code “C” (A = WMO “3 and 5 rule”; B ≥ 25 years; C ≥ 20 years; D ≥ 15 years of data). An average is not a guarantee: a late frost is still possible.

Probabilities

10%25%33%50%66%75%90%
Spring frost (0 °C or lower) on or afterMay 13May 8May 5April 30April 27April 25April 19
Fall frost on or beforeSeptember 30October 10October 12October 16October 20October 26November 3
Frost-free period ≤ (days)139161162165180183191

Example: the spring 10% column is the date after which a frost occurs in only one year in ten.

Indicative planting calendar

Start tomatoes, peppers and eggplant indoorsMarch 4 – March 18
Sow peas, spinach, lettuce and radish outdoors (frost-tolerant)April 1 – April 15
Plant potatoes and onion setsApril 15 – April 29
Transplant tomatoes and peppers; sow beans, corn, squash and cucumbersMay 6 – May 20
Last sowing of quick crops (radish, lettuce, spinach)September 4 – September 19
Harvest or cover frost-tender cropsOctober 12 – October 19
Plant garlic and spring bulbsOctober 19 – November 16

General gardening rules of thumb computed from this station's average last/first frost dates; they are not ECCC data. Adjust to local conditions and seed-packet instructions.

Nearby stations

Chatham Wpcp · 185 dIlderton Bear Creek · 160 dNew Glasgow · 163 dLondon Int'l Airport · 164 dSt Thomas Wpcp · 152 dWindsor A · 195 d
Sources & licences

Environment and Climate Change Canada — Canadian Climate Normals 1981–2010 (station data, MSC Datamart) (30-year averages; not updated). Retrieved 2026-10-18 19:10 UTC.
Data Source: Environment and Climate Change Canada Environment and Climate Change Canada Data Servers End-use Licence.

OpenCanadaData is independent and is not affiliated with or endorsed by these data publishers. Always check with the official source before you go.

Independent. OpenCanadaData is an independent website. It is not affiliated with, endorsed by, or acting on behalf of the Government of Canada or any government body. Original data is available free of charge from the official sources linked on each page.