ATHENS — Greek authorities on Friday warned of an impending weeklong heat wave during the summer tourist season, with a high risk of dangerous wildfires, as much of southern Europe sweltered under high temperatures.

The ministry for civil protection and climate change said southwesterly winds from Africa would bring temperatures sometimes exceeding 40 degrees Celsius (104 Fahrenheit) at least until July 19.

The new heat wave comes on the heels of the hottest June on record in Greece, according to preliminary weather service data. It was also the hottest globally, according to the European climate service, Copernicus.

People have been advised to wear light clothing, drink plenty of water and avoid long hikes during the hottest part of the day. In June, several tourists were found dead on Greek islands after setting out on long walks.

In neighboring North Macedonia, authorities have also issued a weeklong heat alert starting Friday in the small, landlocked Balkan country.

People were urged to stay indoors when possible and avoid heavy labor in the hottest hours of the day. Emergency measures announced Thursday include ordering employers to keep pregnant women and people aged over 60 off work, banning construction work from 11 a.m. to 5 p.m., and keeping kindergarten classes indoors after 11 a.m.

Health officials have reported a rise in calls to emergency responders due to heat-related health problems.

North Macedonia’s authorities also reported an increase in wildfires, saying 14 were registered nationwide in the past 24 hours.

Wildfires are also plaguing Greece, and the civil protection ministry has warned of a very high risk on Friday and Saturday. Officials have described this summer as the most dangerous in the past 20 years for wildfires, following an unusually rainless winter and spring that have left vegetation and forests tinder-dry.

Three fires broke out Friday in northern Greece, although two of them were quickly brought under control.

Greek firefighters, backed this summer by drones and a strengthened fleet of water-bombing aircraft, have dealt with more than 2,000 wildfires since the beginning of June. Most were tamed shortly after they broke out, which limited damage to buildings or property.

Dozens of people have been arrested and fined for accidentally starting fires, mostly during outdoor work near uncleared vegetation.

Every summer sees devastating wildfires in Greece, and last year more than 20 people died in the blazes.