The World Meteorological Organization (WMO) said it is monitoring a heat wave through much of the Northern Hemisphere, exemplified by a soon-to-be record-long stretch of heat in Phoenix and raging wildfires in Greece. According to the WMO, the heat wave is expected to intensify this week throughout “the southern United States, Mediterranean, North Africa, Middle East and some countries in Asia, including China.”

“If there are any new extreme temperature records during the ongoing heatwaves, we will issue a quick preliminary assessment and then start detailed evaluations as part of our painstaking verification process,” WMO Weather and Climate Extremes Rapporteur Randall Cerveny said in a statement. “Climate change and temperature increase has spurred a surge in reports of record weather and climate extremes, especially for heat. We have to make sure that these records are verified for the sake of scientific understanding and accuracy.”

Tuesday, July 18, was expected to be the 19th straight day the city of Phoenix sees temperatures soar to 110 degrees Fahrenheit or higher. The record of 18 days above 110 that was tied Monday, July 17, was first set in 1974. It looks like it will be shattered, with temperatures in Phoenix forecasted to stay above 110 through the end of the week.

Nighttime has offered little relief from the brutal temperatures. Phoenix’s low of 95 degrees on Monday was its highest overnight low ever, toppling the previous record of 93 degrees set in 2009. Monday marked the eighth straight day of temperatures not falling below 90 degrees, another record.

According to the National Weather Service (NWS), record-breaking heat is expected to continue in the Southwest, the lower Mississippi Valley, and parts of Florida.

“Daytime highs will reside in the triple digits in the Desert Southwest and Texas. The Gulf Coast and Mid-South can expect daytime highs in the upper 90s that coincide with oppressively high dew points, resulting in sweltering heat indices between 105-115. Daily low temperatures will remain quite warm, breaking record warm daily minimums in some areas, allowing for minimal relief from the heat overnight,” the NWS said Tuesday. “An expansive area of Excessive Heat Warnings and Heat Advisories remains in the Southwest, Southern Plains, western and central Gulf Coast, and even parts of South Florida where well above normal sea surface temperatures and lighter than normal winds are contributing to stifling heat.”

While Phoenix deals with the heat, a fire swept uncontrolled through Greece Tuesday, one of several wildfires in the country in recent days. While Firefighters managed to contain blazes southeast and west of Athens, residents north of the Greek capital were urged to evacuate as another fire was still active.

Those not in the path of Greece’s wildfires still had to contend with a heat wave in the country. The famous Acropolis areological site was temporarily closed last week due to the heat.

“The truth is that we had many incidents today, for sure more incidents today than yesterday, we had fainting, people feeling dizzy, and some elderly people that couldn’t walk well, they needed shade and we tried to provide them with everything they needed at that moment,” Red Cross officer Stella Katsoulopoulou said Friday, July 14.

In addition to monitoring for record heat, the WMO issued a warning that said heat could lead to an increased risk of heart attacks and deaths. The organization focused on record nighttime temperatures, calling it “particularly dangerous for human health, because the body is unable to recover from sustained heat.”

“While most of the attention focuses on daytime maximum temperatures, it is the overnight temperature which will have the biggest health risk,” extreme weather and climate specialist John Nairn said Tuesday. “The recently declared El Nino is only expected to amplify the occurrence and intensity of extreme heat events. So we’re in for a bit of a ride, I’m afraid, and they will have quite serious impacts on human health and livelihoods.”