BALTIMORE (WJZ/AP) — Baltimore City public schools are operating on a half-day schedule due to a heat advisory in effect for the region.

The schools will be dismissing early on Tuesday, and half-day afternoon pre-kindergarten classes have been canceled. However, all field trips and after-school activities will go on as scheduled.

Baltimore County schools will close three hours early Tuesday. Click here for a full list of school closings.

The National Weather Service says temperatures are expected to be in the 90s. It has issued a heat advisory for the area from noon until 8 p.m.

The Baltimore City Health Department has also declared a Code Red heat alert, and officials are opening cooling centers and reaching out to vulnerable populations. Click here for more information.

(Copyright 2011 by The Associated Press. All Rights Reserved.)