The National Weather Service has issued a freeze warning for Brown and surrounding counties from 4 am to 10 am Friday.

Temperatures are expected to quickly drop after sunset this evening, eventually dropping to below freezing for portions of The Concho Valley, Heartland, northwest Hill Country, and the Northern Edwards Plateau.

Topography will be critical tonight and will largely determine just how cold temperatures fall at your location. The coldest locations will be in the lowest lying locations such as the San Saba and Llano river valleys, near creeks and streams, and along lake shores. In these areas, temperatures will fall into the mid and upper 20s.

Across much of the remainder of the area, including the city of San Angelo itself, readings will be a few degrees warmer, but will still drop into the upper 20s and lower 30s. Areas along Hilltops may even be a few degrees warmer still with readings in the mid and upper 30s.

Ranchers with cattle or livestock should avoid areas where Johnson grass may have been exposed to these cold temperatures.

A freeze warning means sub-freezing temperatures are imminent or highly likely.

These conditions will kill crops and other sensitive vegetation.