What an autumn edition means for the Total 24 Hours of Spa weather forecast?

14 October 2020

Since it was announced that this year's Total 24 Hours of Spa will be staged on 22–25 October, the weather has been a frequent topic of conversation among fans.

On one hand, this is nothing new: the weather is always a major aspect of the race for competitors, marshals and fans alike. Rain, in particular, is as much a part of Spa's character as Eau Rouge or the Ardennes.

But the move to an autumn edition has elevated weather talk to new levels. The consensus is that this year's race will bring more rain than ever before, and there has even been talk of snow falling on Spa-Francorchamps during race week.

Are these predictions correct? We dug into the data to see what the 2020 Total 24 Hours of Spa might have in store. 

Temperature

Let's start with the obvious stuff: clearly, this year's race will bring lower temperatures than we have been accustomed to. The average for July is 18.4°C, while in October it is 14.9°C. In terms of highs, the July average is 23°C compared with 19°C in October, so it will certainly be a few degrees cooler at the autumn edition.

Temperature changes have a meaningful impact for competitors. This is not immediately evident from TV footage, and so it is rarely a major topic of conversation, but the engineers will certainly be paying close attention.

Speaking of temperatures, last year's race was a scorcher. The mercury rose into the high thirties during race week, giving Spa an almost tropical feel. Then, on race day itself, the heavens opened and the circuit was drenched. This leads nicely to our main area of interest... 

Rain

Spa wouldn't be Spa without rain. The circuit alone is demanding enough, but it is the local microclimate – which can see showers at one end of the track and sunshine at the other - that makes the 24 Hours a truly unique challenge.

It rains every month in the region, so we certainly can't rule out a wet race this year. There is, however, a crucial difference. The kind of deluge that follows a period of intense heat – as we saw in 2019 – does not tend to occur in autumn. October rain is usually lighter and more persistent, very different from the torrential variety witnessed during the summer months.

As such, July has an average precipitation level of 73.5mm, compared with 68.9mm in October. The average number of rain days is lower in July (14.3) than October (15.7), meaning more is falling in a shorter amount of time. This is explained by the national average thunderstorm days in each month: while October has 7.7, July has 13.3. In fact, October is a relatively dry month in the region around Spa-Francorchamps, comparable in terms of both rainfall and temperatures with April.

So rain is still a distinct possibility this year, while thunderstorms are less likely. Despite this, there will be no shortage of Pirelli tyres making their way to the Ardennes in October.

Snow

The weather has thrown down some significant challenges in recent years, from stifling heat to torrential rain. What we have not faced, however, is snow. Such an occurrence has been all but impossible, with the 24 Hours traditionally run in July or occasionally August. But does the move to October mean we could be building snowmen in the paddock this year?

Statistically, it is unlikely. In Belgium, the months between May and October do not tend to see meaningful snowfall. It is most common from December through February, with an average of five snow days per month, so if the 24 Hours ever stages a Christmas edition we may need to consider 4X4 GT3 cars. March, April and November also see some snowfall, with roughly 2-3 days in each.

We can conclude that October is more likely to see snowfall than July, though you don’t need to study any data to work that out. It isn't especially likely, but you can be sure that this information will factor into pre-event preparations. So, does Pirelli produced a snow tyre?

Final Forecast

Even by studying trends from previous years, we can't predict exactly what is in store three months ahead of the race. In fact, it is often difficult to predict what will happen in three minutes at Spa. Nevertheless, the statistics tell us that this year's event will be cooler, with less likelihood of thunderstorms and a very small chance of snow.

Regardless of what unfolds, the weather is certain to add an extra layer of interest to what promises to be a fascinating autumn running for the Total 24 Hours of Spa.

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