Heatwave and drought would reduce French growth by 0,1 points in 2026

The economic consequences of heat waves and drought are beginning to be quantified. During a hearing organized on September 2, 2026 by the National Assembly's fact-finding mission on the cost of the heat wave, the Directorate General of the Treasury and the National Institute of Statistics and Economic Studies (Insee) assessed their impact at 0,1 point of gross domestic product (GDP) over the whole year.

This estimate could weigh on the 0,7% growth forecast currently held by the Government for 2026. It is based mainly on the expected sharp decline in agricultural production.

Agricultural production in sharp decline

According to representatives of the Directorate General of the Treasury, agricultural value added, which measures the wealth created by the sector, is expected to decrease by 8% in 2026. This decline would represent about half of that observed during the heat wave of 2003, a year in which agricultural value added fell by about 15%.

INSEE also estimates the economic effect of the heat waves of summer 2026 at 0,1 point of GDP, compared to 0,3 point during the heat wave of 2003.

This impact, however, is already largely reflected in the first-half economic results. The latest national accounts show a 0,2% decline in GDP in the first quarter, followed by zero growth in the second quarter. The carry-over growth for 2026 now stands at 0,3%.

“There is no real additional impact to be expected at the end of the year,” stated Dorian Roucher, head of the economic forecasting department at INSEE. The institute counts agricultural production during crop growth, not at harvest time.

Corn, grasslands, and vegetables were particularly affected.

The consequences vary greatly depending on the crops. The Ministry of Economy forecasts a 35% decrease in corn production in 2026 compared to 2025. As of August 10, cumulative grass growth was also a third below normal, which notably affects the availability of fodder for livestock.

Wheat harvests, on the other hand, appear to have been less affected. According to INSEE, yields remained close to normal thanks to an early harvest.

The decline in some production is already impacting prices. Fresh vegetables saw an increase of around 14%. Dorian Roucher estimates that this increase contributed 0,1 percentage point to the 2,4% inflation rate recorded in August.

In addition to these climatic effects, there are the consequences of the conflict in the Middle East. The rise in gas prices has increased the cost of producing nitrogen fertilizers, while the closure of the Strait of Hormuz has disrupted part of the global fertilizer trade.

A third of public works companies hampered by the climate

The building and public works sectors have also been exposed to the intense heat, which can lead to adjustments in working hours, the interruption of certain tasks and a decrease in productivity on construction sites.

According to the quarterly survey by INSEE and the National Federation of Public Works , 33% of public works companies reported in July experiencing difficulties related to adverse weather conditions. This proportion reached a level not seen since April 2018.

These disruptions nevertheless occurred in a sector that was already weakened. In July, 56% of the companies surveyed reported difficulties related to insufficient demand, while order books were considered particularly depleted.

It therefore remains difficult to precisely isolate the portion of the decline in activity attributable solely to heat waves. Furthermore, work that was interrupted or slowed down may be made up for in the following months, thus limiting its impact on annual GDP.

Construction already declined in the first half

INSEE's detailed national accounts show that construction output fell by 1,7% in the first quarter of 2026, then by 0,3% in the second quarter. Investment in construction, for its part, declined by 2,1%, then by 0,2%.

These figures reflect a deteriorating economic situation but do not allow us to attribute this trend solely to weather conditions. Weak demand, financing constraints, and the slowdown in public and private investment are also weighing on activity.

Costs that extend beyond just lost growth

The Minister for Ecological Transition, Monique Barbut, estimated in mid-August that the successive heat waves could represent between 10 and 15 billion euros in direct and indirect costs for France.

This assessment covers a broader scope than the effect on GDP: damage to infrastructure and heritage, destruction of stocks, health expenditures, emergency interventions or even productivity losses.

The consequences are also expected to weigh on public finances. With the 2027 budget bill due to be presented on September 30th, the government has already warned that its objective of reducing the public deficit to 5% of GDP by 2026 will be difficult to achieve.

The National Assembly's fact-finding mission is continuing its hearings in order to simultaneously assess the cost of the damage and the cost of the adaptation measures needed for agriculture, buildings, infrastructure and working conditions.