For temperatures we usually use the Blatchford weather station which is located near downtown Edmonton. If you are interested in how temperatures differ between Blatchford and the International Airport, that's covered here.
For precipitation the Blatchford station is missing a few years of recent data, and so for today we will mostly be using the data from the International Airport. If Blatchford's numbers are available then they will be included for comparison.
Precipitation History
We are going to start with this chart, which shows the precipitation (rain & snow) at the International for each year going back to 1995. It's impossible to read any numbers off of it, but it looks neat.
What is nice about this chart is that it shows just how much our precipitation ramps up during the May-August timeframe, and in comparison how low the winter months are. We will see that reflected in a lot of the other charts today, and this shows how consistent that is, year after year.
Now lets look at some numbers...
Monthly Precipitation
To get things started this chart shows the precipitation totals for each month of the year.
This chart uses a format that we will be seeing a few times today, with the recent average as a white line in the middle, and it is surrounded by a grey band for the 25th-75th percentiles (where things will fall roughly half of the time), and that is surrounded by the recent extremes in green and yellow (highest, second highest, second lowest, and lowest since 1995).
The blue line in this chart is the precipitation for 2018 at the International Airport, the green line is Blatchford, and the red line is the International's 2017 number for comparison.
In 2018 September was the International's most precipitation-y month at 79mm, and was just a touch below September 2006. June was 2nd and right around average, while July was in 3rd and just below the 25th percentile. That's a little strange, because July is typically our month with the most precipitation, with June in 2nd place. The last time that September was the month with the most precipitation was 2006 with 80mm. The last time that July wasn't 1st or 2nd was in 2008 when it was in 4th spot with only 36mm.
For Blatchford's numbers some of the months were a close match to the International, while others - like May & September - were much lower. Blatchford was above the International in January, April and July, but only by a tiny amount - July was Blatchford's biggest lead, but that was only by 3mm with 65mm vs 68mm.
And looking back to 2017, April was very high, and September was also quite high that year but not as high as 2018.
Days with Precipitation
This chart shows the number of days each month on which we had precipitation. The number of days with precipitation at the International in 2018 is in Blue, for Blatchford it is green, and the 2017 at the International it is red.
We just saw that September had a lot of precipitation, and it also had a lot of days with precipitation. At the International there were 18 days and at Blatchford it was 13, while the average for September is only 9 days. The International's 18 days were more than any September at the International, and they tied Blatchford's record of 18 days for September 1934 and 1996.
For the other months of the year April, May & June were all a little low coming in just a bit below the 25th percentile, and November was just a bit above the 75th percentile.
Looking back to 2017, April and November were both quite high, while December was very low.
Cumulative Precipitation
Here we have all of the precipitation added up across the year for the International and Blatchford.
The International's 463.5mm was just a bit above average, while Blatchford was 105mm lower at 357.9mm. Following the blue and green lines in the chart a large gap opens up between them in May, and that grows bigger in September and November.
A similar gap between the stations happened in 2017 too, with the International recording 489.6mm while Blatchford was 114mm lower at 376mm. And that might be accurate...or it might reflect a problem with the Blatchford station.
Yearly Precipitation History
This is the yearly precipitation totals for the International, going back to 1961.
The International's 463.5mm for 2018 is down a bit from 489.6mm in 2017 and 496.3mm in 2016. It is still at the high-end of our recent range though, and above years like 2014 & 2015 which were down around 350mm.
Back in the 1960s through the 1990s totals in the 500-600mm range weren't uncommon, but since about 2000 our average precipitation has dropped a bit.
Here we are looking at precipitation totals each year, but this time we have Blatchford (1880-2007) and the International (1961-today). In this chart there is a green section which is shaded slightly darker for the years 1961-2007 when both stations had reliable data. That darker section is the difference between the two stations, and in some years Blatchford was higher, while in others it was the International.
Blatchford's 2 years with the most precipitation were 1900 & 1901, and they were way up at 745mm and 699mm respectively. We have never seen anything else like that though, and Blatchford's #3-5 years are all in the range of 618-650mm, which is around where the International's top years are too.
Looking at the 5-Year average in red, from about 1900-2000 it was pretty consistently between 400-500mm. Since 2000 our average precipitation has dropped by about 50mm to the 350-450mm range, which we had originally looked at here. And before 1900 there were a bunch of low years, and that might be accurate, or that earliest data might have some problems.
Earlier we saw that for both 2017 & 2018 Blatchford had recorded 100mm+ less precipitation than the International. Historically a large gap like that was not typically the case, with the two stations being fairly close to one another. So for Blatchford's low precipitation in 2017 & 2018:
- possibly Blatchford just had two really low years in a row
- possibly something has fundamentally changed at Blatchford
- or possibly the data has problems
Rain & Snow
And finally for today, here is how our precipitation is split between rain & snow each year.
We average around 400mm of total precipitation, and snow is just about one-third of that at 130cm (Environment Canada usually converts 1cm snow = 1mm precipitation). That split has stayed fairly consistent going back to around 1900. And this year it was 464mm of precipitation with 167cm of snow...or about one-third.
We are going to leave things there for today, but we will have a whole bunch more charts dedicated to snow in Part 3 in a few days.
If you are wondering what previous Precipitation years-in-review looked like:
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