After a stormy but even-temperatured spring, the official start of summer — Friday, June 20 — is bringing a heat wave with it. The National Weather Service has issued an extreme heat watch for St. Louis County and city from Saturday afternoon to Tuesday.

In the first heat wave of the year, temperatures are expected to rise to the mid-90s. Heat indices could be 98 to 106 degrees, according to meteorologists. 

Humidity will rise over the weekend, causing dangerous conditions for prolonged outdoor activities — particularly in the afternoon, when heat indices could surpass 100 degrees on Saturday, Sunday and Monday.

Experts recommend staying hydrated, minimizing time outdoors and wearing lightweight clothes when outdoors.