Nest Hub devices got an update last summer that has added a local air quality rating to the home screen, next to weather. Now after just few weeks ahead of summer 2022, Google added similar feature to Maps: a map of the air quality ratings in your area which is accessible from layer menu.
Google announced the change about an year ago and the air quality ratings range from zero ro 400+, with lower numbers being better. In order to view the ratings in Google Maps app you are required to tap the layers icon located near the top right corner and after that select the Air Quality under Map details. The data comes from the government agencies like EPA, Purple Air and Google says. It adds a Maps layer that shows live weather data were intended to launch in near future. It seems like Google is a bit late and you will see the weather layer in near future.