Interestingly, there is no universal definition in terms of “how high.” It’s based on the region and the time of year. Temperatures have to be outside the historical averages for a given area.
For example, an average day in in North Africa near the Mediterranean Sea would be regarded as heat wave conditions in England and Northern Europe.
That said, we often think of a heat wave typically lasting two or three days or more—and generally 10 degrees or more above average.
Interestingly, there is no universal definition in terms of “how high.” It’s based on the region and the time of year. Temperatures have to be outside the historical averages for a given area.
For example, an average day in in North Africa near the Mediterranean Sea would be regarded as heat wave conditions in England and Northern Europe.
That said, we often think of a heat wave typically lasting two or three days or more—and generally 10 degrees or more above average.