The National Weather Service San Diego issued a heat advisory Thursday morning covering inland San Diego County valleys, including Santee and other East County communities, effective from 10 a.m. Thursday through 8 p.m. Friday.

A strengthening high-pressure system combined with easterly winds is driving the unseasonably warm weather. Thermometers in Santee and the surrounding inland valleys are expected to reach the low-to-mid 90s on both Thursday and Friday — 20 to 25 degrees above the typical mid-March average. Coastal communities will see readings in the low-to-mid 80s.

"Hot temperatures may cause heat illnesses," the NWS advisory states. Forecasters are urging residents to drink plenty of fluids, stay indoors in air-conditioned spaces when possible, avoid extended sun exposure, and check on elderly neighbors and family members.

The weekend will bring some relief, though temperatures are expected to remain above normal. However, forecasters warn that an even more intense heat event is possible next week, with the potential for all-time March temperature records to be broken at some locations across the San Diego region.

Residents with medical conditions sensitive to heat, young children, and anyone working outdoors should take extra precautions during the advisory period. The San Diego County Office of Emergency Services advises limiting strenuous outdoor activity to early morning or evening hours through the end of the week.