Answer: See map below.
Click on the map to see detailed rain charts for each basin.
The long-term dry season average, as calculated from November 1st to April 31st, is about 12 inches ... although that number varies from basin to basin. The critical spring months coming up next probably matter most. No rain coming in plus increasing water going out (i.e. escalating evaporation and plan transpiration) can drop the water table down quick, cascading us downward into deep spring drought.
If only we could hold onto the surplus water from our abundant summer rains, that wouldn't put us in the perilous pinch of praying for perfectly-timed precipitation come spring.
We've got to find ways at being better at that.