Travel and holiday interests: extreme heat alert 15th-19th July southeast England, France, Benelux

Off the top I want to underline that this alert does not apply to Ireland on current guidance, and the highest temperatures expected for parts of Ireland around next weekend would be 26-28 C, which is considered hot but not extreme.

The heat developing over France all week is likely to spread into southern England, Belgium and some other parts of western Europe around next weekend. The peak of the heat would be Sunday 17th - Monday 18th on present guidance. Extreme values are possible, with numerical guidance showing values of 41-42 C in southeast England and 44-45 C in Paris and much of northern France, Belgium.

If you had travel or holiday plans that take you into those regions during that time period, I would advise that you monitor these forecasts and consider an alternative plan, and if you're there now consider an earlier return possibly, I would think by Thursday or so, to avoid this extreme heat. Having gone through the "heat dome" situation we had in western Canada (and the northwest U.S.) last summer, it's not just an uncomfortable heat, it can threaten your health and safety. In those regions there are few air conditioned indoor spaces, just as was the case here (air conditioning is common further south, but not in our region because normally a heat wave here has tolerably cool nights and homes do not heat up to dangerous temperatures, in the heat dome, we were seeing hundreds of cases of heat prostration, and of course incendiary fire conditions in the forests and grasslands).

This is an alert rather than a warning, weather models are not perfect but if the numerical output now available is correct, these temperatures are sure to follow, and there will be an emergency situation that you don't want to dabble with if you don't need to (and who else but MTC could manage two dangling prepositions in one sentence? Sacre bleu).

I am reminded of the 2003 heat wave in Paris which briefly impacted southeast England too, but not quite as full on as this may do, also this is worse looking with Paris topping out closer to 42 C in August 2003.

So this thread can now also be used to discuss the extreme heat potential and track what actually happens. I hope it turns out less extreme but I have to report that we had a similar look on our weather guidance here about a week before the severe heat set in (late June 2021) and even though the guidance was essentially correct, most professional forecasters slightly underestimated how hot it could actually become until it hit in full force. At my location, we had three days near 44 C and the previous extreme value all-time was 39 C, so it was that far outside the normal range.

Between now and about Friday of next week, conditions in northern France and southern England will not be all that extreme but it will be sunny and hot, bone dry, so when and if this extreme heat develops, the ground will already be very dry. There would be quite a risk of grass fires, one cause of them can be when overheated vehicles come into contact with dry grass (another cause is when goofballs throw out cigarette butts, is that still a thing in Europe? sadly it is over here) and then also you have cases of arson by those with criminal intent.

If you're in England long-term and wondering how widespread this could be, it looks more tolerable from about B'ham to Leicester to Lincoln north and west, most of north-central England and Wales would top out around 31-34 C, southern Scotland likely 28-32 C.

Nights will not provide a lot of relief in the main heat zones, even if lows do fall to around 20-22 C like they did in our heat dome situation, the relief is too brief to make any impact on indoor temperatures. We found it very difficult to keep indoor temperatures below 32 C even with all windows open all night. It would fall off to maybe 27 C by dawn then start rising again.