San Joaquin Valley
A basin closed on three sides — which is why it is the driest, hottest and haziest air in the state.
The southern Central Valley is enclosed by the Coast Ranges, the Sierra Nevada and the Tehachapis, with one real opening at its north end. Storms arrive already wrung out by the Coast Ranges, so Bakersfield takes about six inches a year — genuinely semi-arid — while the Sierra crest 60 miles east takes ten times that. The same enclosure traps everything else: winter inversions hold cold, fog and particulates against the floor for weeks, and the valley owns some of the worst air quality in the country as a matter of terrain rather than of behaviour.
- Elevation range
- 0 ft → 500 ftHigh point: valley floor throughout
- Relief
- 500 ftTop to bottom, inside this region
- Span
- 161 × 235 miEast–west by north–south
- Annual rainfall
- 5–13″Driest to wettest ground here
- Köppen types
- BSkCsa8 counties
Map of San Joaquin Valley within California.
The four seasons here
NOT A GENERIC SEASON WITH THE PLACE NAME SWAPPED INWinter
Fog and low cloud under a strong inversion. Cold by California standards, and stagnant.
Spring
Brief and pleasant; the inversion breaks and the valley greens for a few weeks.
Summer
The hottest sustained heat outside the deserts. Bakersfield and Fresno both average near 99°F in July.
Autumn
Clear and warm well into November before the first fog sets up.
Places in this region
4 PLACES, LOWEST FIRST| Place | Elevation | Jan high | Jan low | Jul high | Jul low | Annual precip | Snow |
|---|---|---|---|---|---|---|---|
| Stockton | 13 | 58° | 39° | 95° | 61° | 17.3″ | — |
| Modesto | 88 | 56° | 39° | 95° | 63° | 12.3″ | — |
| Fresno | 308 | 55° | 41° | 98° | 69° | 11.0″ | — |
| Bakersfield | 404 | 58° | 40° | 98° | 71° | 6.4″ | — |
National Parks in this weather region
FIELD NOTES FROM THE PARK TRANSECTTerrain and gradients
WHAT THE ELEVATION ACTUALLY DOESRanges and passes
A PASS IS A WIND FEATURE FIRSTWho forecasts it
OFFICIAL FORECASTS AND WARNINGS COME FROM HEREGolden State Weather is not a source of watches or warnings. For those, go to the offices above.