The season so far

In an earlier blog I used satellite imagery to forecast that 2016 would be a heavier than normal grass pollen season.

As the latest BoM images are showing lots of green across the Victorian countryside, my prediction still stands.

Another way of assessing how the season is progressing is by looking at the cumulative total of grass pollen grains. That is, add each daily count to the sum of all the previous daily counts from October 1 – that’s the red line in today’s graph – and compare that line to the cumulative counts for other seasons. The blue line is our average grass season and the two dashed lines are 1993 – our worst season with an eye-watering total of 6,700 grass pollen grains – and 2015, our mildest season with just over 1,000 grass pollen grains.

To put 'worst' and 'mildest' into some perspective, there are 92 days between October 1 and December 31, which is the period we count. So in 1993 the average grass pollen count was over 70 grains per day. That’s well into the high range and on a high day it's likely all people sensitive to grass pollen will experience hay fever symptoms. By comparison, in 2015 the average daily count was only about 11, a number comfortably in our low range of grass pollen counts.  Most people will not experience hay fever symptoms on a low day.

Today was also our first extreme grass pollen day, that's when the daily average was over 100 grass pollen grains per cubic metre of air.  It's our first extreme day since November 28 2013 and users of our app have rated their symptoms today as moderate, that's just one step below our top rating of severe.

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