<p>City officials warned that sweltering temperatures gripping the Chicago area this week pose a significant risk to vulnerable communities, including older residents, people with disabilities, young children and those without access to air conditioning.</p><p>The National Weather Service has issued an extreme heat warning that will remain in effect through Wednesday evening. The heat index — which means what the hot air feels like when combined with humidity — will approach 105 degrees at times.</p><p>The high of the day was 92 degrees around 4:30 p.m. Monday at O'Hare International Airport, where the NWS measures its temperatures.</p><p>"Extreme heat can be very dangerous," said Mayor Brandon Johnson during a morning press briefing at the city's Office of Emergency Management and Communications on the Near West Side.