Is This Weather Normal? – 2018 Overview

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The weather in Terrace, BC for 2018 can be summed up in a few primary stories:

  • A winter story: Higher than average snowfall at low elevations.
  • A temperature story: Warmer than average, and with the 3rd warmest summer on record.
  • A summer/fall drought story: Record-setting dry conditions from July through October.

But first, some annual averages and totals for 2018:

  • 2018 was the 25th warmest year on record, averaging 7.1°C, which is 0.7°C warmer than the 1971-2000 baseline climate.
  • 2018 was the 7th driest year on record, with a total of 934mm of precipitation, which is 439mm below the 1971-2000 average, or 68% of normal.

While these annual values tell part of the story of 2018 weather, they mask some of the truly weird weather that we experienced in 2018. Figure 1 shows average monthly temperature for 2018 (blue dots) in comparison with all years on record. February was quite a bit colder than average, July and August were much warmer than average.

Figure 1: 2018 average monthly temperature for Terrace, BC. The dotted blue curve is 2018, the 10 red lines are the ten warmest years on record, every other year is in gray. The black line is the long-term average, and the error bars mark plus/minus one standard deviation.

A Winter Story:

Conditions in Terrace, BC during the winter of 2018 were noteworthy in that we had a large early snowfall in November (2017) followed by colder than average temperatures and more snow through February, leading to snow persisting through the winter at lower elevations. It was the 31st coldest winter (Dec. – Feb.) on record, with temperatures 1°C below the 1971-2000 average. Even with this cold, and the persistent snow on the ground, it was the 15th driest Dec. – Feb. on record with total precipitation 190mm less than average. This significantly lower than average precipitation (61% of normal) meant that while we had lots of snow at low elevations, the mountain snowpack was unremarkable. Looking at total snowfall for the months Nov. – Mar. reveals that it was the 19th snowiest winter on record in Terrace.

Some noteworthy winter statistics:

  • 13th coldest February (-5.2°C), 3.9°C colder than average.
  • 19th snowiest winter (Nov. – Mar.):
    • 384cm of snow
    • 105cm more than average
    • Well below the record winter of 655cm (1972).

A Temperature Story:

The main temperature stories for 2018 were the much warmer than normal months of July and August, and a record setting temperature for a day in June. While the year was only the 25th warmest on record, we had the 3rd warmest summer (Jun. – Aug.). Average summer temperature was 17.2°C, 1.7°C warmer than average. The month of June was nearly identical to the average, but we then had the 4th warmest July followed by the 3rd warmest August (Figure 1).

Additional seasonal temperature statistics for 2018:

  • 31st coldest winter, 1°C below average
  • 49th warmest spring, 0.2°C above average
  • 3rd warmest summer, 1.7°C above average
  • 29th warmest fall, 0.7°C above average

Just like the annual average temperature masks seasonal and monthly variability, seasonal and monthly averages hide the day-to-day extremes experienced during the year. Figure two shows the average daily temperatures for the year.

Figure 2: Daily average temperature for 2018 in Terrace, BC (red line). The black line shows the 1971-2000 average. The two gray lines show plus/minus one standard deviation.

Changing temperature between the two gray lines (plus/minus one standard deviation) can be considered average variability. When temperatures go below or above these two lines we’re starting to see conditions that are more out of the ordinary. There were a few such events in 2018.

The colder than average February (roughly between Julian day 30 and 60) stands out pretty clearly, with two peak cold days: -13.4°C on February 10th, and -11.8°C on February 19th. Getting cold days like this isn’t out of the ordinary, and in fact we usually get more such days and the minimum temperature in a given year is usually colder. Only two years had the lowest winter temperatures higher than the -13.4°C recorded in 2018. Or, in other words, 28 out of the 30 years during the climate baseline period (1971-2000) had temperatures colder than our coldest temperature in 2018. Translation: It didn’t get that cold in 2018.

The peak temperature on May 18th of 18.4°C (day 138) wasn’t a record setting temperature for the month of May, but certainly was much higher than the average and within a few degrees of the all-time high for the month of May.

The two times of highest average daily temperature occurred on June 19th (25.3°C) and on July 30th (25.1°C). Only two years during the 1971-2000 baseline climate period had an average daily temperature above 25.3°C. June 19th, 2018 set an all-time record for temperature in June with a high temperature of 34.2°C and an average daily temperature of 25.3°C. The peak summer temperatures of 2018 were well above normal.

A Summer/Fall Drought Story:

The final, and most important weather story of 2018 was the July through October drought. It was the driest Jul. – Oct. on record with a total of 150mm of precipitation (37% of normal), and the driest Jul. – Sep. on record with a total of 56mm of precipitation (26% of normal). None of the individual months were record setting, but taken together they are the driest four-month period on record in Terrace.

  • 9th lowest July precipitation
  • 5th lowest August precipitation
  • 4th lowest September precipitation
  • 9th lowest October precipitation

Figure 3: 1913-2018 total precipitation for the months July – August. The long-term average is in black and dashed. There are two years of missing data (1914 and 1953).

The impacts of the 2018 drought will likely linger, unless the region receives well above normal snowfall and a cool/wet summer in 2019. Watch for analysis for January and February 2019 coming to GlacierChange.org soon, followed by updates at the end of each month.

Some weather-related news stories from 2018 for Terrace and the larger region:

Province Increases Drought Rating in Parts of Northern BC, Terrace Standard

Province Ups Drought Level for Coastal BC, Terrace Standard

‘Unprecedented Low Water Levels’ in Northern, Central BC Raise Fears for Future of Wildlife, CBC

Some weather-related links:

Government of BC Drought Information Portal

Terrace, BC Weather Forecast (Environment Canada), All data presented in this post is freely available here.

 

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