On the evening of the 15th, a significant marine push occurred and moved well inland toward the west side of the central San Joaquin Valley as an upper-level trough moved onshore; Pacheco Pass experienced a 42 mph wind gust that evening. That gust prompted a wind advisory that was issued during that evening for the west side of the San Joaquin Valley for Fresno and Merced Counties. Temperatures on the 16th fell several degrees from the previous day, including in the San Joaquin Valley. The trough remained over the region through the 17th. Temperatures were several degrees normal on both of these days, with highs in the central and southern San Joaquin Valley only in the mid to upper 80s for high temperatures, and upper 80s to lower 90s in the desert areas of eastern Kern County.
The upper-level ridge returned to interior central California by the 18th. Temperatures rose to a few degrees above average by the 19th. The weather has remained mainly dry through September 22nd, with mainly cumulus cloud buildups over the southern Sierra Nevada crest.
Off the coast of California, a low-pressure system developed within the ridge and drifted toward the coast. By September 23rd, the flow around this low drew subtropical moisture into southern and central California. The ridge remained the dominant large-scale feature over central California, bringing unseasonably warm weather to the region. Fresno had a high of 101 degrees on the 23rd, the third, and last, time Fresno say triple digits in September. With a very warm and unstable airmass, thunderstorms developed across the region. Although there was moisture in the mid-level of the atmosphere, the lowest levels remained dry, and the thunderstorms were mostly dry with numerous lightning strikes. The lightning triggered several wildfires in Kern County, with a few fires started in Tulare County. Outflow winds from the thunderstorms toppled power poles in northeast Bakersfield, knocking out power to over three thousand people. In the Mojave Desert northeast of Mojave, winds blew a big rig over on State Route 58.
Clouds from the showers and thunderstorms remained over the central California interior through September 24th, keeping low temperatures unseasonably warm. Fresno set record high minimum temperature records on both the 23rd and 24th.
A strong cold front moved into central California on September 25th, bringing sharp drops in temperature. The highs at Bakersfield and Fresno on the 24th were 97 degrees; the next day, the high at Bakersfield was only 80 and Fresno was only a degree warmer. The unseasonably cold airmass lingered over the region the next two days, slowly mixing out. A weak upper-level ridge boosted high temperatures over the central and southern San Joaquin Valley into the mid to upper 90s on September 29th, but highs fell back to near normal the next day. A weak surge of monsoonal moisture at the end of the month brought isolated thunderstorms to the Southern Sierra Nevada crest.
Bakersfield had five days in September with highs at or above 100 degrees, and Fresno had 3 triple-digit days. For the summer, through the end of September, Bakersfield had 30 days with highs at or above 100 degrees, while Fresno had 28 days. The average temperature for September was 80.3 degrees at both Bakersfield and Fresno. This was the third warmest September on record for Fresno, while Bakersfield tied for its ninth warmest September on record.

Thunderstorm Wind in KERN, CALIFORNIA
From 23-SEP-11 17:40:00 to 23-SEP-11 17:40:00 (PST-8)
Location: BAKERSFIELD EAST
Magnitude: 50.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A severe thunderstorm toppled a tree and a power pole. In Bakersfield 3723 customers lost power.

Thunderstorm Wind in KERN, CALIFORNIA
From 23-SEP-11 18:15:00 to 23-SEP-11 18:34:00 (PST-8)
Location: CHAFFEE
Magnitude: 50.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A big rig was blown over in Highway 58 near mile marker 170 due to a severe thunderstorm wind gust.