Axios

Earth recorded its hottest day on record on Thursday, making it the fourth straight to set or tie the record for warmest day globally.

Why it matters: The daily records are a symptom of the heat that human emissions of greenhouse gases are adding to the climate, combined with an El Niño event in the tropical Pacific Ocean.

At least 45% of U.S. tap water is estimated to be contaminated with "forever chemicals," according to new U.S. Geological Survey research.

Why it matters: Exposure to certain levels of these synthetic compounds, referred to collectively as PFAS, has been linked to adverse health effects in humans and animals, including an increased risk of cancer.

The past three days have each broken or tied records as the Earth's hottest day since at least 1979 and likely far longer, according to National Oceanic and Atmospheric Administration data, accessible via a University of Maine website.

Why it matters: Daily temperature milestones are largely symbolic — but point to an alarming trend, scientists say.