The National Weather Service has issued a red flag warning of increased fire risk for parts of the Berkeley and Oakland Hills extending from Friday morning through 9 a.m. Saturday, due to a combination of high winds, low humidity and warm temperatures. An excessive heat warning also remains in effect.

Parts of Tilden, Claremont Canyon and the Berkeley and Oakland Hills at elevations above 1,000 feet are under the warning, NWS meteorologist Nicole Sarment said. The Berkeley apartments are not included in the warning.

“The greatest risk will occur during the night between Friday and Saturday,” reads the Berkeley Fire AC Alert for the red flag warning.

The excessive heat warning, first issued by the NWS on Tuesday, has been extended until 11 p.m. Saturday because the heat is “just stagnant over us” and there are no other weather systems around to dissipate it, Sarment said.

The weather service predicts temperatures in downtown Berkeley will reach 88 on Saturday and 87 on Sunday. Tilden could reach 93 on Saturday and 90 on Sunday.

The temperature is expected to drop next Tuesday.

The NWS issues a red flag warning every time Conditions are ripe for wildfires. All the signs are there: hot, dry and windy weather, combined with a “predominant overnight dry spell” that brought humidity levels to as low as 1% in some parts of the Bay Area last night, Sarment said.

(On some of the red flag days when conditions create “particularly high-risk conditions,” Berkeley Fire will declare extreme fire conditions. No warning had been issued at time of publication.)

On Red Flag days you should follow this advice:

• Keep your phone on, charged and in your pocket all day.
• Fill your tank with gas and pack your trunk with your go bag and extra water. Be aware that garage doors powered by electricity may not open, but avoid parking on the street.
• Avoid activities that could cause a spark, such as parking or driving over dry vegetation, which is a common cause of fires this year, Sarment said. Make sure you extinguish cigarettes and barbecues properly and follow local fire bans and fireworks bans.
• Be prepared for rapid evacuation if necessary.

A Spare the Air Warning, issued by the Bay Area Air Quality Management District when concentrations of ozone pollution or smog are expected to be unhealthy, remains in effect through Saturday. Bay Area residents are encouraged to limit driving.

Berkeley recommends going to a public library, senior center, or other air-conditioned space if your home gets too warm. Due to the extreme heat, the Tarea Hall Pittman South Branch Library, which is normally closed on Sundays, will be open this Sunday from 10 a.m. to 6 p.m., according to the city’s AC Alert. The Live Oak Community Center is open this Saturday and Sunday from 11am to 6pm. Both locations are air-conditioned.

A spokesperson for the East Bay Regional Park District did not immediately respond to a request for comment. Check the district’s park closure website before you go. As of Friday afternoon, Tilden Park and Claremont Canyon Regional Preserve appeared to remain open, but the district has closed trails in the past when fire risk is high.

Berkeley Fire offers the following safety tips for red flag days:

• Sign up all your devices for AC Alert.
• Leave your phone turned on to receive alerts even when you’re sleeping, and don’t use Do Not Disturb mode during risky weather conditions.
• Berkeley’s emergency card:
• Download the Genasys Protect app to receive real-time alerts about any status changes or emergencies in those zones.
• Find your evacuation zone on the Berkeley Emergency Map website, referenced in AC Alert evacuation notices. (Example: “BER-E044” is Berkeley Zone 44) and learn more about the city’s emergency alert tools, such as our new outdoor alert system.
• Place your go-bag at the front door.
• Plan multiple evacuation routes, including two on foot.
• Park off the street. Reverse your car in your driveway or garage to keep the streets clear for emergency vehicles.

This story was updated after publication with information from the City of Berkeley.