2017: 2nd Hottest Summer on Record

August 25, 2017

7pm Friday

Today has been a wonderful day once again with slightly warmer temperatures; we made it into the lower 80s around the metro area

PDX Observed High Today

Of course August is just about finished with just 6 days to go.  It’s been a hot month across most of the Pacific Northwest, but nowhere else in the USA.  Note that if you take the country as a whole, it’s a relatively cool month.


This is after a slightly warmer than normal July and a warm May + June.  That cool spell from December through April is just a memory now…we’re back into the warm regime that hung over the West Coast for about 2 and a half years.

With only 6 days left to go in Summer, at least meteorological summer and a pretty solid forecast, we can take a look at the stats.  This is likely going to end up as Portland’s 2nd hottest summer on record!  Remember many of us (including me) thought that maybe a summer following a weak La Nina winter might be normal or a little cooler than normal.  That sure didn’t work out.

MarkSummer WrapUp

Are summers getting warmer around here?  Most definitely YES!  Take a look at PDX average temperatures June-August from the late 1930s through this year, a rise of about 3 degrees in that nearly 80 year period.  That’s pretty dramatic.  I even heard a radio talk show host yesterday say that we are cooling, or “some scientists think we are cooling” in the Pacific Northwest.  Where that comes from I don’t know.


Note the last 5 very warm (or hot) summers.  Clearly there is some cyclical climate action going on over the years (warming and cooling), but we are warming and most likely it’s directly related to human-caused global warming.  No, the sky isn’t falling so far in the Pacific Northwest and it’s not the end of society here.  My garden loves this weather and outdoor water activities are thriving.  But you should be aware that we ARE warming and assuming that continues even more people will want/need air conditioning in the future west of the Cascades.  Of course water supply is a much bigger issue, this summer has been even drier than normal, in a place that doesn’t get much rain in summer anyway.   If this is the future we’ll need to store more of that winter rain and snowmelt.  There will be changes in our local vegetation if the warming continues as well.  Look at the difference between Portland and Roseburg as you drive down I-5 as an example.  It’s hotter down there in the summertime and drier too.  Now before you get hung up on the fact that nights are warming faster in urban areas (they are) than rural areas and that skews the graph a bit, note that even the daytime highs have been rising at a similar rate.  Afternoon highs are not affected as much by the heat island effect as overnight lows are.


Since there can’t be too many charts in a weather blog…here you have Astoria’s summer temps since records began at the airport in the early 1950s…warming but at maybe half the rate at a station that is not urbanized and right beside the chilly Pacific.  Interesting eh?


Looking ahead now…the last week of August and first week or so (at least) of September appear to be real scorchers for this time of year.   It’s because upper-level ridging wants to hang over the West Coast in one form or another through the next two weeks as it has most of this month.  The ECMWF model’s ensemble forecast of 850mb temperatures.  That’s the temperature at 5,000′ over Portland in celsius:


The green line is the average for this time of year…wow, the entire period is well above average.  You can see two obvious peaks both in the ensembles and most of the operational run as well.  The first is this coming Sunday/Monday, then again right over Labor Day Weekend.  These will be the hot periods, with more reasonable, but still warmer than normal temps the 2nd half of next week.  This is very bad for our native shrubs/trees which will have gone over 2 months with no substantial rain.  They may end up going 3 full months without a soaking.  Even in our dry summer climate that’s a bit extreme.  Only 15 of all 51 ECMWF ensembles produce 0.10″ of rain or more into the 2nd week of September.


The GFS model and GEM are similar showing the ridging over the next 2+ weeks like the ECMWF monthly run from last night:



So keep watering all your shrubs and maybe even some trees too.  Summer 2017 is definitely not finished yet.

Chief Meteorologist Mark Nelsen