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Ontario · climate station 6116750 · 480.1 m

Proton Station

Average last spring frostMay 31
Average first fall frostSeptember 16
Frost-free period107 days

1981–2010 normals; ECCC quality code “D” (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 afterJune 25June 12June 9May 31May 28May 27May 19
Fall frost on or beforeSeptember 1September 7September 9September 16September 19September 23September 26
Frost-free period ≤ (days)769398105112117123

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 indoorsApril 5 – April 19
Sow peas, spinach, lettuce and radish outdoors (frost-tolerant)May 3 – May 17
Plant potatoes and onion setsMay 17 – May 31
Transplant tomatoes and peppers; sow beans, corn, squash and cucumbersJune 7 – June 21
Last sowing of quick crops (radish, lettuce, spinach)August 2 – August 17
Harvest or cover frost-tender cropsSeptember 9 – September 16
Plant garlic and spring bulbsSeptember 16 – October 14

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

Thornbury Slama · 152 dHanover · 124 dFergus Shand Dam · 151 dAlliston Nelson · 149 dGlen Allan · 148 dOrangeville Moe · 132 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 19:09 UTC.
Data Source: Environment and Climate Change Canada Environment and Climate Change Canada Data Servers End-use Licence.

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