These plots show the start and end of the dry season in the western US. Essentially the dry season starts after the winter rains end. A second factor is max temperature which is presumed to cause more evaporation according to a linear formula. Higher temparatures also cause a more intense dryness during the dry season (future work). There are some complications. There can be a false start to the dry season where the rains stop but pick back up. There's an adjustable parameter for the dry interlude. Beyond that period any rains that occur are not considered to "restart" or end the dry season.

Sacramento's dry season is starting earlier by about 2 weeks per century. Santa Barbara is starting earlier by 18 days per century and lasting 5 days longer (per century) in the fall. However on the east side of the state, Nevada City's dry season is starting later and ending earlier. Kentfield CA just north of San Francisco has a dry season shifted slightly earlier.

In Oregon the trends are not as clear. In some locations the dry season is ending later. In one location it is starting later. Any changes seem to be location-dependent.

Code: dryseason.py | Data: california.csv, oregon.csv | Instructions: README