How to read the Météo France fire risk prevention map?

A new tool requires new reflexes. Meuse and Meurthe-et-Moselle were the first departments placed on Monday, June 12, on orange alert due to a high risk of forest fires, according to the new indicator from Météo France. Moselle, Paris and Hauts-de-Seine were also concerned for Tuesday. Then, on Monday evening, the alert was lifted. But what exactly do these different levels of risk mean?

Météo France launched its “forest weather forecast” on Friday, for educational purposes. The objective is to inform the French about the risk of fire and the behavior to adopt to prevent fires from occurring in the forest massifs, while more than 785,000 hectares of forest have gone up in smoke in France. in 2022.

A familiar color code

The forest weather color code (green, yellow, orange and red) is based on that already in force at Météo France to differentiate the levels of vigilance when approaching meteorological phenomena and their associated risks (floods, storms, heat wave, strong winds, etc.). The division is done at the level of the department and not at the level of the forest massifs. Green represents danger “weak” of “start and spread of forest and vegetation fires”, while red indicates a “very high risk”.

The difference is that these are not vigilance cards. “Forest weather does not provide information on current or future fires (unlike ‘storm vigilance’ for example, which is a forecasting device”, insists Météo France, which designed it as “a tool for raising awareness and preventing the risk of fire danger”. So, “a department can be placed in orange, but not be affected by fires in the end, if precisely the reflexes of prevention are well respected”. Conversely, “a low level of danger does not mean the absence of a fire risk in the department”.

On this simulation carried out a posteriori for the day of July 18, 2022, we see that the west of France was particularly vulnerable. However, fires or resumptions of fires also took place in other areas: that same day, firefighters were fighting to contain a fire in Savoie, a department represented in green, therefore exposed to danger. “weak”. Also, the level of risk “pupil”, in orange, maybe “locally very high”.

Instructions to limit the risks

At each level are associated recommendations intended for the general public. As recalled byhe Minister of Ecological Transition, Christophe Béchu, “90% of fires are of human origin and more than half come from stupid gestures: cigarette butts, barbecues, grinders”.

Météo France therefore recalls the basics to avoid the outbreak of fire, in the absence of prohibitions issued by the prefecture of your department. Install your barbecue on a terrace away from the vegetation, do not smoke in the forest and get rid of your cigarette butts in an ashtray. Bring a fire extinguisher if you carry out work outdoors and store flammable products and materials (wood, gas cylinders) in a closed shelter, away from your home.

Finally, in the event of a fire starting, the instruction is to alert 112, 18, or 114 for the hearing impaired, to take shelter in a cleared house (especially not in a car) and to s inform of the instructions issued by the emergency services or the town hall.

Any access bans and closures of forest areas will be available from the prefectures of the departments concerned. “Failing to comply with the prevention instructions issued by the public authorities exposes you to a 4th class fine of 750 euros”recalls in passing Météo France.

Weather forecasts crossed with observed drought conditions

The risk of forest fire is established by Météo France “from observations and forecasts of several meteorological parameters and the state of drought of the vegetation”. weather conditions “strongly influence the sensitivity of vegetation to fire, both for the start of fires and for their spread”, explains the forecaster. It lists the cross-referenced parameters to determine the risk: rain, air humidity, temperature, wind strength and finally the state of dryness of the vegetation, which “is a aggravating factor”.

“We often talk about the rule of 30: you need a temperature of more than 30°C, a wind of more than 30 km/h and soil humidity below 30%”summarizes Sébastien Thomas, journalist for France Télévisions in the Meteo-Climate service. “If you have these three factors, the risk of fire is very high.” However, global warming linked to human activities accentuates this risk by increasing the intensity of some of these criteria. For example, heat waves are becoming longer, more frequent and more intense, which contributes to drying out vegetation.