The Delta variant, which has become the more predominant variant in the U.S., is likely the reason for the recent rise in cases and hospitalizations in the county.
A high level means 100 or more cases per 100,000 people in that county.
DuPage and McHenry counties were also determined to be high transmission areas.
Since the onset of the pandemic, Lake County has reported 63,340 cases of the coronavirus along with 1,030 deaths.
For more information about when to get tested for COVID-19 and the types of tests available, visit the CDC's website.
To find testing locations in Lake County, visit the county's vaccine portal.