Western Europe experienced its hottest June-July period on record as extreme heat, drought and wildfires continued to affect large parts of the Northern Hemisphere, the World Meteorological Organization (WMO) said Tuesday.

Spokesperson Clare Nullis told reporters in Geneva that July was also the joint second-warmest July globally, with average surface air temperatures 1.47C (2.6F) above the estimated pre-industrial level.

Sea-surface temperatures were the “highest ever recorded” for July, she said.

Nullis said some Western European countries are facing their fourth heat wave of the summer, while prolonged drought is affecting agriculture, river levels, transport and energy, and increasing wildfire risks.

Meteo-France expects temperatures above 35C in much of France later this week, while MeteoSwiss has issued a Level 3 alert for temperatures exceeding 35C. Parts of southern England could reach 36C by Thursday, according to the UK Met Office.

The WMO’s climate information chief John Kennedy said the pattern reflected the combined effects of long-term warming and persistent high- and low-pressure systems.

He warned that extreme heat is becoming more frequent, more intense, longer-lasting and more widespread.

WHO spokesperson Tarik Jasarevic told reporters that wildfire smoke poses a major public health threat, particularly because of fine particulate matter.

He said exposure is associated with premature deaths and can cause or worsen diseases affecting the lungs, heart, brain and nervous system, skin, kidneys, eyes and other organs.

Jasarevic added that firefighters and emergency workers face particular risks from burns, injuries and heavy smoke exposure, while children, older adults, pregnant women and those with chronic illnesses are especially vulnerable.