Observing campaign number 21 starts off as run 20 ended: rain and thunderstorms. The atmosphere was incredibly unstable. The night started off reasonably clear and several objects were successfully observed, but photometry was impossible for nearly all of the targets as small clouds formed and dissipated on time scales of just a few minutes. After only 2 hours of observing, rain started falling from the smallest of clouds and the dome was barely closed in time. Conditions worsened extremely fast and the observatory had to be prepared for a band of thunderstorms that quickly moved through the area before midnight. Seeing during the relatively short portion of the night that was useful was quite good (1-1.5 arcsec).