WJZ meteorologist Tim Williams has the Thursday midday weather update.

The National Weather Service has issued a freeze warning for the Baltimore area west of Interstate 95 overnight Thursday, with temperatures expected to drop as cold as 30 degrees.

The warning is in effect from 3 a.m. through 10 a.m. Friday. It covers Harford, northern Baltimore, Carroll and Howard counties and points west.

Forecasters cautioned that unprotected plants could be killed or damaged. For those who don't have gardens or crops to worry about, the warning is a sign that it might soon or already be time to turn on the heat.

As of 2 p.m. Thursday, temperatures hadn't risen above 53 degrees at Baltimore-Washington International Thurgood Marshall Airport.

Downtown, temperatures had reached 55 degrees by 2 p.m. The urban heat island effect kept Baltimore City and suburbs around it in southern Baltimore County out of the freeze warning zone, with overnight lows forecast in the upper 30s.

Partly cloudy skies and some sunshine are again expected on Friday, and another dip toward freezing temperatures is expected overnight into Saturday morning.

For the weekend, highs are forecast in the mid- to upper-60s with lows in the upper 30s and lower 40s and mostly clear skies Saturday but increasing clouds Sunday.