Montreal McGill Weather Records (CA007025280)

The annual mean temperature here has risen by 0.2 C (0.2 to 0.3) per decade over 1872 to 1983. In Fahrenheit: 0.4 F (0.3 to 0.5) per decade. The slope is a straight line fitted to 111 complete years; the brackets give its 95 percent interval.

Across 111 years with a frost, the median last spring frost at Montreal McGill falls on 25 April and the median first autumn frost on 18 October, which leaves a median of 176 days between them.

In 1954 to 1983 the median growing season was 186 days. That is 15 days more than in 1872 to 1902.

Fitted over all years, the growing season changes by +1.8 days per decade at this station.

A day with at least 48.5 mm (1.9 in) of rain is expected about once in 2 years. A day with at least 100.0 mm (3.9 in) of rain is expected about once in 100 years.

The levels come from a generalised extreme value (GEV) distribution fitted by L-moments to the wettest-day total of each year, 112 years of values from 1872 to 1983.

A return level is an estimate. It is least reliable for the long periods, 50 and 100 years, and for any period longer than the record behind the fit, where the fit has to reach past the largest day actually observed. It is not a forecast.

The largest wettest-day totals in the fit: 90.4 mm (3.6 in) in 1958; 87.6 mm (3.4 in) in 1880; 86.1 mm (3.4 in) in 1932.

2 changes were suspected in the annual mean temperature of Montreal McGill, at 1917 and 1953. Each is measured against neighbouring stations.

• Relative to 5 neighbouring stations, the station's annual mean temperature from 1917 ran 0.2 C (0.3 F) lower than in the years before (possible change).
• Relative to 5 neighbouring stations, the station's annual mean temperature from 1953 ran 0.3 C (0.5 F) higher than in the years before (likely change).