SOUTHLAND MUGGED BY TROPICAL WEATHER, RECORD HIGHS.

Byline: Sherry Joe Crosby Daily News Staff Writer

Records fell again Monday as triple-digit heat scorched Los Angeles for a third day in a row, triggering a tornado in the San Gabriel Valley, widespread power outages, an all-time high for electricity usage, and violent thunderstorms.

Records for the date were broken in Chatsworth, where the mercury reached a blistering 108, and in Simi Valley, where it was 104. It was 106 in Woodland Hills, 104 in Van Nuys and 101 in Burbank.

Forecasters said only slightly cooler temperatures are expected today.

The unusual tropical weather had widely different consequences, including downed power lines and trees after a tornado touched down near the 605 and 210 freeways to the flash floods in Big Bear and a brush fire near La Crescenta. It rained in Thousand Oaks and thunderstorms and power outages plagued the Antelope and San Fernando valleys.

Thermometers reached 100 in Lancaster and 104 in Palmdale where a violent thunderstorm knocked out power, churned up dust clouds, sparked at least one brush fire and dropped hailstones a half-inch in diameter.

``It's so loud you can hear it on the roof,'' Alis Clausen, Southern California Edison district manager, said from Edison's office at 10th Street West and Avenue M. ``It looks like ice out of a soft drink.''

Over a 24-hour period, the Los Angeles Fire Department responded to 25 heat-related emergencies, spokesman Jim Wells said Monday afternoon.

``Anytime there's a heat wave we get an increased number of exposure calls,'' said Wells, who cautioned residents to stay indoors, curtail their activities during the hottest part of the day and to drink plenty of liquids.

Northridge resident Dietricha Sweeney took salt tablets, ate potassium-rich potatoes and kept a water bottle by her side Monday - to avoid a heat stroke, one of which she suffered five years ago from similarly intense heat.

``The last couple of days, it's been horrendous,'' Sweeney said. ``It's hellish and very oppressive. I hope it breaks soon. You're sort of wilted and it zaps your ability to think.''

Los Angeles Police Department Officer Richard Todd shared Sweeney's sentiments, only the Valley Traffic Division motorcycle officer was weighed down in a required helmet, knee-high boots and a bulletproof vest.

``It's brutal heat,'' said Todd. ``Plus, we have the heat from the engine. We have no chance to cool down like in a car. The air is so warm.''

In the city of San Fernando, the 1400 block of Hewitt Street was without electrical power from 6:30 p.m. Sunday until 9 a.m. Monday, prompting police and city officials to canvas the street to check on a large group of elderly residents who live there, said Sarah Magana-Withers, the city's community preservation officer.

Department of Water and Power spokeswoman Darlene Battle said customers used electricity at an all-time level Monday. The utility distributed 5,640 megawatts of power, breaking the previous record of 5,520 megawatts set Sept. 4, 1997.

While Monday's sweltering temperatures caused scattered power outages for about 200 customers, including 75 in the Valley, Battle said the utility does not foresee brownouts. It is recommending, however, that customers conserve energy during the hottest part of the day.

At California State University, Northridge, where the afternoon temperature peaked at 104, several students congregated under a patio umbrella to compare summer notes and class schedules, but quickly opted to move the meeting into the air-conditioned game room.

``It's just too hot outside, even in the shade I can feel myself burning up,'' said 23 year-old Noel Rodmen, a CSUN senior.

Among the victims of the latest heat wave was Andrew Perry, a 23-year-old Northridge resident who spent Sunday, sans sunscreen, at a local water park. Blisters and red skin highlighted his second-degree-burned face.

``I should've known bett`er, I just forgot to put sunscreen on this time,'' the emergency medical technician lamented. ``I'll probably be paying for this little episode for the rest of my life.''

Forecasters said a slight cooling trend was expected today with temperatures anticipated to drop five degrees during the next few days in the Valley. A decrease in humidity levels also was forecast.

``It won't feel much cooler in the San Fernando Valley,'' said Vladimir Ryshko, a meteorologist with the National Weather Service. ``It will be slightly cooler on Wednesday, otherwise it will still be warm.''

Higher and higher

The triple-digit highs Sunday marked the West Valley's 23rd day in 1998 that temperatures hit or passed 100 degrees

West Valley -- 108 degrees

23 -- Number of day 100 degrees or hotter this year

30 -- Average number of days at or above 100 degrees in a year

63 -- Most days at or above 100 degrees in a year

East Valley -- 101 degrees

10 -- Number of days 100 degrees or hotter this year

8 -- Average number of days at or above 100 degrees in a year

21 -- Most day at or above 100 degrees in a year (in 1979 and 1983)

Daily News Staff Writers Brooke Olson, Yvette Cabrera, Charles F. Bostwick and Lisa Van Proyen and The Associated Press contributed to this story.

CAPTION(S):

Photo, 2 boxes

PHOTO (color) Lightning strikes near the San Gabriel Mountains on Monday during an unusual convergence of weather phenomena, including high humidity, hail and a tornado.

Nick Ut/Associated Press

Box: (1) Higher and higher (see text)

(2) L.A.'s high: 108 degrees in Chatsworth on Monday