Seasonably warm days ahead, with frequent rains | Forecast

Today is the first day of meteorological summer (June-August), and it is expected to usher in a week of generally above-normal temperatures that will probably extend well into the following week. A west-to-east jet stream flow aloft over the United States is a good indicator that colder Canadian air will be held well to the north. Illinois will rest on the northern flank of warm air centered over the southern United States. Expect brief clearing intervals between extensive periods of cloudiness and showers and thunderstorms associated with frequent low pressure systems.