I've been teaching a landscape class in San Francisco and its been a challenge but a fun experience.  With the constantly changing light and unpredictable weather conditions, painting in plein-air is always a challenge.  Fortunately, the weather has been unusually mild in San Francisco and so the following painting was completed over two days with fairly consistent weather.  The light pattern was changing as it fell across the dome but in general not too difficult conditions.  Both days I painted in the afternoon from around 1:30pm to 4::30pm. 
Degas described painting in plein-air as the "tyranny of nature" and in some ways I can see what he means.  Its difficult trying to capture something in a more unique way than what we are all used to seeing.

Day Two: Palace of Fine Arts, 12" x 16" oil on linen panel "Not quite finished but I think I'll leave it this way."