10 p.m. CDT
Tropical Storm Bill already is having an effect on classrooms in Texas.
School districts in Galveston and in southern Houston suburbs canceled classes for Tuesday. Houston school district officials said late Monday they had not made a decision but were monitoring the weather closely.
The eastern half of Texas is under flood watches, with up to 10 inches of rain expected in some areas. The southeastern quarter of the state is under a watch through Wednesday, while the northeastern quarter is under a watch from Tuesday through Thursday.
9:25 p.m. CDT
Tropical Storm Bill has formed in the Gulf of Mexico and is expected to make landfall in flood-besieged Texas by morning.
The National Hurricane Center in Miami said Monday night that Bill was centered about 160 miles (260 kms) east-southeast of Port O'Connor, Texas, and about 155 miles (250 kms) south-southeast of Galveston, Texas. A tropical storm warning is in effect for the coast of Texas from Baffin Bay to High Island.
Bill had maximum sustained winds of 50 mph (85 kph) and was moving northwest at about 12 mph (19 kph). On the current forecast track, the storm would make landfall along the Texas coast Tuesday morning before moving inland over south-central Texas on Tuesday afternoon and Tuesday night.
The center said some slight strengthening is possible before landfall. Bill is expected to weaken after moving over land.
6 p.m. CDT
A storm sweeping across northern Illinois has prompted a tornado warning and forced the cancellation of hundreds of flights at Chicago's airports.
The National Weather Service issued a flash flood watch for northern Illinois. Forecasters say the storms are expected to dump up to 2 inches of rain per hour at times.
The weather service issued a brief tornado warning for Chicago's western suburbs. Warning sirens prompted downtown Chicago office buildings to warn tenants to shelter in hallways away from windows. There are no immediate reports of injuries or damage.
The Chicago Department of Aviation is reporting delays of up 30 minutes at O'Hare International Airport, where more than 430 flights were cancelled. Delays of 35 minutes and the cancellation of 25 flights are reported at Midway International Airport.
5 p.m. CDT
Dallas streets and highways closed by floodwaters over the Memorial Day weekend are expected to be closed again in anticipation of a new round of heavy rain.
Officials Dallas officials to activate the city's Emergency Operations Center on Tuesday. The decision is based on National Weather Service forecasts of potential rainfall of 7 to 10 inches Tuesday night through Thursday morning.
The center hopes to plan well enough ahead that areas expected to be hard-hit by floodwaters can be evacuated well in advance of the threat.
City crews will begin pre-staging street barriers Tuesday morning in anticipation of those closures.
4:20 p.m. CDT
Authorities in Norman, Oklahoma, say a mother, her child and others were rescued from high waters following a short and intense downpour.
Norman Deputy Fire Chief Jim Bailey says responders on Monday afternoon rescued the occupants of three vehicles that stalled out in high water. It is unclear how many people were rescued from the vehicles but Bailey says there were no injuries.
He says the vehicles became stuck in low-lying areas that couldn't drain fast enough but that much of the water has since receded.
National Weather Service Meteorologist Jonathan Kurtz in Norman says the area received heavy rainfall that lasted about 30 minutes. It wasn't immediately clear how much rain was dropped by the storms.
4:15 p.m. CDT
Houston officials say they're activating the city's Emergency Operations Center at 6 p.m. Monday.
The center will coordinate the responses of all city departments to a tropical disturbance headed toward the Houston-Galveston area.
Activities to be coordinated by the center will include those of the city's police, fire, health and public works departments.
Also being activated will be the Catastrophic Medical Operations Center to coordinate potential resource or information needs are required by hospitals in a 25-county region.
2:30 p.m. CDT
Texas Gov. Greg Abbott has ordered elevated activation of the Texas State Operations Center. That's as a tropical disturbance in the Gulf of Mexico was expected to intensify and move toward the Houston-Galveston area.
A statement from Abbott's office on Monday says the governor also has approved the use of state resources staged for rapid deployment as needed to help local officials deal with the storm.
Abbott noted that in the wake of recent floods from heavy rains, "any additional rainfall will exacerbate already saturated grounds, which could quickly lead to dangerous flash flooding and extended river flooding."
The National Weather Service says it expects the disturbance to intensify and begin affecting the Texas coast as early as Monday night.
1 p.m. CDT
Galveston County officials are recommending people on the low-lying Bolivar Peninsula leave in anticipation of high water and heavy rains from a storm brewing in the Gulf of Mexico off the Texas coast.
County Judge Mark Henry issued a voluntary evacuation Monday as an alert that emergency responders may not be able to reach people if forecasts are correct that the sliver of land across from Galveston in Southeast Texas could get up to a foot of rain. The storm is expected to hit sometime Tuesday, with an expected landfall farther down the Texas coast.
A ferry to Galveston is the most common access to the peninsula, but service could be halted by winds and high tide.
Most structures on Bolivar were wiped out in Hurricane Ike in 2008.