The National Weather Service issued an Extreme Heat Warning for Carlsbad and San Diego County coastal areas, with temperatures expected to reach the low 90s near the coast starting Friday, Oct. 2.

The warning runs from 10 a.m. Friday, Oct. 2, through 8 p.m. Thursday, Oct. 8, according to the NWS San Diego office. The agency described the conditions as dangerously hot, with coastal highs in the mid-80s to low 90s and higher terrain along the mesas reaching the mid-90s to 100 degrees. Overnight lows will hover in the low to mid-70s, making it harder for residents to cool down at night.

"This will be the longest heat wave with temperatures this hot in years," NBC 7 San Diego Chief Meteorologist Sheena Parveen said. NBC 7 meteorologist Brooke Martell said high pressure building over the region, combined with easterly winds, is driving the heat even at the coast. Inland valleys could see highs between 100 and 105 degrees.

The city of Carlsbad designated the Carlsbad City Library at 1775 Dove Lane as a Cool Zone where residents can escape the heat. San Diego County operates 33 Cool Zone locations countywide, including branch libraries and community centers.

The city urged residents to schedule outdoor exercise for early morning or evening and take frequent breaks. The San Diego County Office of Emergency Services said signs of heat illness include dizziness, nausea, confusion, heavy sweating, headaches and fainting. Anyone experiencing those symptoms should seek help immediately.

The county also warned that fans alone are not enough when temperatures exceed 90 degrees. Older adults, children, people with chronic conditions, pregnant individuals and outdoor workers face the highest risk.

Do not leave children or pets in parked cars. The NWS warned that car interiors reach lethal temperatures within minutes.

SDG&E notified about 35,000 customers in inland and eastern San Diego County that their power could be shut off between Friday, Oct. 2, and Monday, Oct. 5, due to wildfire risk from the heat and Santa Ana winds, Fox 5 San Diego reported. The affected communities are all inland, including Fallbrook, Poway, Ramona and Julian.

Carlsbad is not among the areas facing potential shutoffs.

NWS Oxnard meteorologist Rose Schoenfeld told the Los Angeles Times the heat wave does not have a clear cutoff, with weather models suggesting extreme heat could stretch into mid-October.

Residents can sign up for emergency alerts at AlertSanDiego.org. The Carlsbad City Library Cool Zone is open during regular library hours.