Every month I post an update on how the weather has been, based on the statistics we have kept since 1998. To see the other weather posts, please click on ‘Weather’ under the Topics tab in the right-hand sidebar.

The Statistics Freak considers that summer runs from 1 May to 30 September; five months, in other words. Given the weather sometimes, you could be forgiven for thinking that it was still winter. But I can reveal to you in this post how this summer compares with those of the previous 12 years.

First, the usual update on the past month.

1.     Weather assessment for September

A quick reminder of our subjective weather assessment: we assign each day a plus if it’s fine, a minus if it’s bad and a zero if it’s indifferent or we can’t decide. In September, there were:

Pluses – 19
Zeros – 5
Minuses – 6

The graph shows the percentage of plus days each September for the past 13 years (the line is the trend). September had been improving. In fact, it was one of the better months of the year with consistently fine weather, but this one was not particularly good. Six Septembers were better and six worse than this one.

2.     September rainfall

Our rainfall stats go back to August 2004. This September was slightly drier than the average over this period with 64.5mm (average 68.3mm). It rained on 8 days compared with the average of 6.7 days for September.

This September has not been particularly warm. We don’t collect temperature stats, but the last week or so of September seemed unseasonably cool. We even put the central heating on a couple of times in the past week.

September 22 was the day of our last swim for this year. It was 21C in the pool, which is at my lower tolerance limit. The pool cools down at night and the daytime sun isn’t warm enough to heat it sufficiently now.

Summer 2010

Weather assessment

And the summer overall? The table* below shows the percentage of days that were pluses, minuses or zeros for the period 1 May to 30 September 2010, compared with the average for 1999 to 2010 (12 years’ worth of data). This shows quite clearly (as if we didn’t know already) that this summer was worse than average. 33 days had bad weather over that five-month period. If this were an average year, you would expect 21 days to have bad weather.

*Sorry, folks, WordPress doesn’t seem to like imported tables, so here’s the data in a less digestible format:

Percentage of plus days: 2010 – 58.5%; average – 62.5%
Percentage of 0 days: 2010 – 15%; average – 21%
Percentage of minus days: 2010 – 21.5%; average – 14%

Rainfall

However, the amount of rain we had over the summer was astonishingly close to the average for that period since 2004:

May – September 2010  – 318.5mm
Average May – September, 2004-2010 – 318.1 mm

This does mask the fact that the distribution of rainfall during summer 2010 was quite different from the average (see the chart below). Wetter than average May and June were followed by drier than average July, August and September. (You’ll also notice from the chart that April, which was the best on record, was significantly drier than normal.)

And finally, something to really cheer you up. Polish weather forecasters are predicting that this winter will be the worst for 1,000 years. Better start breaking out the woolly jumpers and getting in the wood.

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