All of northern Illinois and northwest Indiana is under a flood watch on Wednesday as heavy rains are expected throughout the day, beginning in the morning.

The watch begins at 10 a.m. and is effective until the afternoon for Boone, DeKalb, McHenry, Ogle, Lee, and Winnebago counties.

However, the watch is extending into the evening for Cook, DuPage, Ford, Grundy, Kankakee, Kane, Kendall, La Salle, Livingston, Iroquois, and Will counties in Illinois, along with Benton, Jasper, Lake, Newton, and Porter counties in Indiana.

Showers and thunderstorms are expected to begin in the morning with the strongest storms capable of dropping up to 2 inches of rain in an hour in the hardest hit areas, the National Weather Service said.

Forecasters said there is a threat for possibly two rounds of severe weather on Wednesday, with the first wave beginning in the morning. The second round, with the potential for more dangerous storms, is expected to arrive in early afternoon and last until around 9 p.m.

Conditions will be favorable for fast-moving severe storms bringing not only heavy rains but the chance of hail, damaging winds, and even tornadoes, forecasters said.

Soil moisture is already high, and stream flows are elevated in many areas, so heavy rainfall could quickly result in flash flooding of streams, creeks, low-lying, and flood-prone areas, the weather service said.

A flood watch for flash flooding means rapid-onset flooding is possible, but not yet certain, based on the latest forecasts.

Flash flooding is a dangerous situation. Persons with interests along area rivers, creeks, and other waterways should monitor the latest forecasts and be prepared to take action should flooding develop.