Austin heat waves are longer

Data: EPA ; Note: New York City, Houston, Minneapolis-St. Paul and Denver are excluded for incomplete data in this period; Chart: Axios Visuals

New data shows the upward march of heat waves in the U.S.

The big picture: The EPA info, part of a wider new report on climate metrics, shows heat trends in the 50 largest U.S. metro areas.

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• Heat waves are becoming longer, more frequent and more intense.

Zoom in: Often defined as "a persistent period of unusually hot days," our Austin heat waves last two more days, on average, than in the 1960s.

How it works: EPA tracked events of two or more consecutive days when daily, humidity-adjusted temps topped the 85th percentile of historical July-August temps in 1981-2010.

The bottom line: "Heat waves are more than just uncomfortable," the EPA authors write, "they can lead to illness and death," as well as damaging crops and increasing wildlife risk.

• "Unusually hot days and heat wave events are a natural part of day-to-day variation in weather. As the Earth's climate warms, however, hotter-than-usual days and nights are becoming more common," they observe.

Full EPA analysis