Extreme heat facts and tips for coping in Phoenix.
Weldon B. Johnson/

Yep — about 10 days too early. But even if that temp is reached, forecasters don’t consider it excessive.

It could hit 100 degrees in Phoenix this weekend.

Too soon, right?

You’re right — it’s too soon by about 10 days. The average date of the first 100-degree day of the year is May 2 and the normal high this time of year is 87 degrees.

However, the National Weather Service isn’t planning to issue any excessive heat watches or warnings this weekend.

Simply put, it’s going to be hot but not excessively so, said National Weather Service meteorologist Paul Iñiguez.

“The heat risk will be moderate this weekend,” Iñiguez said. “Some people could experience some negative outcomes from that if they don’t take proper precautions, but we’re not going to issue any warnings in this situation. (Temperatures are) too low for that to happen.”

The Weather Service looks at the historical temperature data for a given date and location when determining whether to issue an excessive heat watch or warning. Generally speaking, the expected high would have to climb into the 95th percentile for that date and location to trigger an advisory.

For example, a high temperature of 100 degrees in late April or May doesn’t qualify as excessive heat but a high of 110 degrees would. That 110-degree high probably wouldn’t trigger a warning in July.

Though this weekend’s highs aren’t expected to get into excessive-heat territory, don’t ignore the risks. This early in the year people haven’t had time to acclimate to 100 degrees and should take precautions to avoid heat-related illness.

Those engaging in strenuous outdoor activity should try to avoid the hottest part of the day, drink plenty of water and take frequent breaks in the shade.

The Weather Service has a website that helps people assess heat risk throughout the Southwest. The site features a color-coded map that assigns a risk level based on factors including temperature and time of year. The site can project risk for a week based on the NWS forecast.

“We’ve been developing this tool for a couple of years now,” Iñiguez said. “It takes our numerical forecast and provides context with it, essentially. Will (heat risk) be more on the high side or something not so much of a concern?”


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