The ongoing yellow heat alert has been extended to 11.59pm on Friday, and now covers the entirety of the Grand Duchy.
MeteoLux predicts temperatures of up to 32°C until Saturday and warns of possible heat fatigue in the case of prolonged exposure or physical activity in this weather.
In France, however, warnings are being extended as the country experiences what has been described as an "unprecedented" heatwave for the month of May. An orange heat warning will apply to 13 departments on Wednesday and Thursday.
According to Météo-France, temperatures could reach highs of 39°C. Young children and elderly people are being urged to take particular care in such conditions.
On Tuesday, the weather service recorded a new national temperature record for May, with a national heat index of 24.8°C, after the previous record of 24.6°C had only been set on Monday. Temperatures in France are currently around 10 to 15 degrees above seasonal averages.
In addition to the nine departments already under heat warning on Tuesday, four more departments in western France, namely Deux-Sèvres, Charente, Charente-Maritime, and Gironde, were added from midday on Wednesday.
Several French cities recorded new temperature highs on Tuesday, including Besançon with 32.2°C and Dinard with 33°C. On Wednesday, temperatures of between 30°C and 35°C are expected, with local peaks of 38°C to 39°C in Poitou-Charentes, Centre-Val de Loire, and around the Mediterranean, according to Météo-France.
French Health Minister Stéphanie Rist said the situation was not yet an emergency, but that there were already warning signs. Seven people have reportedly died due to the heat, including two people at sporting events in Paris and near Lyon, she said. The French government has urged people to avoid such events over the coming days.
A new temperature record was also recorded in the UK. At Kew Gardens in London, temperatures reached 34.8°C on Tuesday, the highest ever recorded in the UK in May.
