Most hospitals in the Bay area offer "per diem" (4+ shifts a month) positions for nurses like that. The going rate is from $60-80 per hour depending on your shift, experience and position. $70/hr x 12hr shifts x 6 days = $5k gross.
But, yeah. Hospitals nation wide are chronically short of staff and California is certainly no exception. Gigs like that are fairly easy to come by if you work it right.
A lot of hospitals are willing to work with you and schedule you all in a row like that if they know you. Many nurses come to the Bay area as a contract nurses on a 3 month contract. They develop a relationship with a department or manager, and then sign on as a per diem and arrange their schedule so they work 6 shifts in a row at the end of one pay period and the beginning of the next one.
I think there will be more and more of this since there is such a disparity in pay between nursing wages in the South and wages in the Bay and in California in general. A nurse in Alabama can work their heart out for $20-25 an hour taking care of 6-8 patients at a time in the ER, while the same nurse in California will make 2-3 times that and care for no more than 4 patients at a time (state mandated staffing ratios).
Staffing ratios mean that hospitals have to maintain minimum staffing levels and if they don't they get in trouble with the state. That means that nursing salaries go up and they're willing to have nurses commute from TX, or Oregon or wherever.