WASHINGTON (7News) — A dangerous heatwave begins today, triggering an extreme heat warning until 8 p.m. This afternoon, temperatures will peak at 102F, while humidity will push the heat index to a staggering 112F. Authorities are advising the public to limit outdoor activity and stay hydrated. In an effort to help keep the public safe, here are some cooling centers throughout the D.C. area WASHINGTON, D.C. All DC public libraries are open and serve as cooling centers.