| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | -0.9° | -8.4° | 66.3mm | 13.7 | 3 |
| February | 0° | -8.2° | 55.3mm | 10.9 | 8 |
| March | 5.5° | -3.9° | 55.7mm | 10.4 | 24 |
| April | 12.3° | 1.6° | 81mm | 12 | 51 |
| May | 19.7° | 7.7° | 80.7mm | 11.3 | 76 |
| June | 24.8° | 13.4° | 100.1mm | 11.4 | 77 |
| July | 27.7° | 16.2° | 83.9mm | 10.6 | 76 |
| August | 26.6° | 15.4° | 76.7mm | 9.6 | 81 |
| September | 22.7° | 11.6° | 77mm | 9.4 | 81 |
| October | 14.9° | 5.6° | 72.9mm | 12.6 | 58 |
| November | 7.8° | 0° | 69.3mm | 11.9 | 34 |
| December | 2° | -4.6° | 66.8mm | 13 | 9 |
January in Markham averages a daily high of -0.9°C with nights around -8.4°C. Expect roughly 13.7 wet days totalling 66.3mm. A hard month to visit for comfort alone.
February in Markham averages a daily high of 0°C with nights around -8.2°C. Expect roughly 10.9 wet days totalling 55.3mm. A hard month to visit for comfort alone.
March in Markham averages a daily high of 5.5°C with nights around -3.9°C. Expect roughly 10.4 wet days totalling 55.7mm. A hard month to visit for comfort alone.
April in Markham averages a daily high of 12.3°C with nights around 1.6°C. Expect roughly 12 wet days totalling 81mm. Demanding conditions — pack for it and plan indoor options.
May in Markham averages a daily high of 19.7°C with nights around 7.7°C. Expect roughly 11.3 wet days totalling 80.7mm. Comfortable conditions for being outdoors all day.
June in Markham averages a daily high of 24.8°C with nights around 13.4°C. Expect roughly 11.4 wet days totalling 100.1mm. Comfortable conditions for being outdoors all day.
July in Markham averages a daily high of 27.7°C with nights around 16.2°C. Expect roughly 10.6 wet days totalling 83.9mm. Comfortable conditions for being outdoors all day.
August in Markham averages a daily high of 26.6°C with nights around 15.4°C. Expect roughly 9.6 wet days totalling 76.7mm. Comfortable conditions for being outdoors all day.
September in Markham averages a daily high of 22.7°C with nights around 11.6°C. Expect roughly 9.4 wet days totalling 77mm. Comfortable conditions for being outdoors all day.
October in Markham averages a daily high of 14.9°C with nights around 5.6°C. Expect roughly 12.6 wet days totalling 72.9mm. Generally workable, with some weather to plan around.
November in Markham averages a daily high of 7.8°C with nights around 0°C. Expect roughly 11.9 wet days totalling 69.3mm. A hard month to visit for comfort alone.
December in Markham averages a daily high of 2°C with nights around -4.6°C. Expect roughly 13 wet days totalling 66.8mm. A hard month to visit for comfort alone.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Markham peaks at 81.
Based on 30 years of records, May–September scores highest for comfort in Markham, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 27.7°C.
June is the wettest, averaging 100.1mm of rain across roughly 11.4 wet days.
January is the coolest month, with average daily highs around -0.9°C.