Northwestern San Diego County got off to a smoky start Thursday after smoke from the Holy fire in Orange County drifted over the region Wednesday night. The weather pattern should clear out the smoke Thursday, but it will only add to the heat. The National Weather Service has issued an excessive heat warning, in effect until 8 p.m. Thursday, from the foothills to the coast. Highs at the beaches could reach the mid 90s, while the inland valleys could be as hot as 104. The culprit is a push of hot air from the east.