Daytime high temperatures will be up to 20 degrees above average in the easternmost reaches of San Diego County on Sunday and Monday, reaching the 103 to 104 degree range in Borrego Springs and 81 to 86 degrees in Ramona, the National Weather Service says.
“Heat-related illnesses increase significantly during extreme heat events. Overexposure can cause heat cramps and heat exhaustion to develop and, without intervention, can lead to heat stroke,” the weather service said in an advisory.
Daytime high temperatures will be roughly average at the coast and as much as 10 degrees above average in the inland foothills and valleys.
Forecasters say the heat, caused by a large high pressure system, will fade by Tuesday. But high temperatures could return late this week.