Why are temperatures rising again in France: how warm and how long?

Forecasters are once again predicting high temperatures for France until at least the weekend, echoing last week’s claims that the mercury could pass 32C in parts of the south west today.

On Monday (September 25), forecasters were less optimistic and gave predictions that daily highs would reach around 23C in much of the country and peak at 29C in the south – but not pass 30C.

Today (September 27), however, temperatures in the south west are set to shoot up, reaching as high as 31C in Bordeaux and 32C in Toulouse.

It comes after some areas recorded temperatures of over 30C yesterday, including a 31.5C high in Les Arcs, Var – a September record

The unusually high temperatures are being caused by residual warm winds from tropical cyclones being pushed into France from the Atlantic.

The warm winds are a classic autumn feature of France’s meteorological profile, said forecaster Régis Crépet, but due to climate change, are becoming hotter and lasting later into the year.

In the rest of the country, temperatures will likely pass 25C every day until next week, except on the extremities of the Breton and Norman coastlines, where temperatures will be lower due to poor weather conditions and rain.

Storm Agnes, which is set to hit the UK and Ireland tonight and tomorrow is the cause of the rainfall, but as of this morning Météo France has not issued any local weather warnings.

Temperatures over 30C likely in south west

Conforming to original predictions from last week, the mercury will remain in the middle or high 20s for most.

In the south, September heat records could be broken this week – the expected 32C in Toulouse is around 8C higher than average recordings for the end of September in the south.

The pocket of warm weather could last until at least the beginning of next week, bolstered by a lack of rainfall and – south of the Loire – cloudless skies.

It means temperatures of over 30C could be recorded in October, with temperatures only set to drop significantly from the second weekend of the month (October 7 and 8).

Read more: ‘Face the reality’: France ‘must prepare’ for +4C global warming

High variation in temperatures throughout the day

The warm weather has been catching many people off guard, particularly in the north.

This is partly due to highs of this level being unusual this close to October – but also because morning temperatures are lower than in the summer despite daily highs being around the same as they were for stretches of June and July.

The minimum to maximum temperature range in some cities differs wildly so it can be difficult to gauge exactly how warm it will be.

For example, whilst highs of 26C are expected in Nancy, the lowest temperature expected in the morning is only 8C, meaning the mercury could climb almost 20C throughout the day.

It is a similar situation in Lyon (10C / 26C) Tours (12C / 28C) and Limoges (13C / 31C).

Even in cities where the mornings are warmer, a difference of almost 15C is expected between 08:00 and 16:00.

The cooler – and longer – autumn mornings mean that there is no risk of any official canicule (heatwave) conditions being declared, as overnight conditions allow fresh air to recirculate and prevent build ups of warm wind.

Read more: France heatwave tips: How to sleep, keep cool and stay healthy

Storm Agnes not expected to cause disruption

Throughout most of the country, no rain is predicted for the rest of the week (and weekend), but in Brittany and Normandy, it is slightly different.

Starting from early this evening and lasting overnight, parts of the coastline will see winds of up to 100km/h as well as rainfall.

This is due to storm Agnes – the first named storm of autumn – which will make its way across the UK and Republic of Ireland overnight.

Warnings are in place across the Channel for strong winds, heavy rainfall, and potential flooding, but in France, no departments have been placed on alert.

Related articles

What to do (and not do) during heavy rain and flood alerts in France