Another La Nina ocean current contributed to December 2017 being colder than normal.
Daily maximum and minimum temperatures ran about 1.3 degrees Celsius below the historical normals, according to Chemainus weather observer Chris Carss.
The first half of the month was mostly dry after the first couple of wet days.
“However, the expected mild spell was intermittent and therefore not enough to keep our average temperatures in the normal range for the month as a whole,” pointed out Carss. “Precipitation returned for the second half of the month as expected, with alternating and sometimes mixed rain and snow.”
Due to the cooler temperatures, Carss added, we had less rain than normal, but above average snowfall that gave most of the Chemainus Valley a White Christmas for the second year in a row.
“The last time we had back-to-back white holidays was just over half a century ago, in 1964 and 1965,” he indicated. “This year’s White Christmas was not anticipated until just a few days before the holiday.”
The mean daily maximum temperature for December was 5.0 C (normal 6.4 C) and the mean minimum came in at 1.1 C (normal 2.4 C). The extreme maximum of 8.0 C occurred on both Dec. 15 and 17 while the extreme minimum of -3.5 C happened on Dec. 24.
Eight days in December were mostly sunny, but Dec. 7 and 8 sunshine was interrupted by fog. This was three more than the normal of five sunny or partly sunny days, according to Carss.
Of the 23 remaining cloudy days, one had fog on Dec. 9 and a total of 13 produced measurable precipitation, eight less than the normal of 21.
The total rainfall for the month was 141.4 mm, well below the normal of 226.9 mm. The total snowfall was 34.0 cm, all of which came during the second half of the month. This was nearly twice the normal of 19.4 cm.