Multiwavelength light curves of 3C   345 for the 20-month period discussed in this paper, from top to bottom for: a) γ rays observed by Fermi-LAT between 0.1 and 300 GeV, values (filled circles) are five-day integrated, 2σ upper limits for five-day integrations are shown as light-blue crosses with downward arrows where TS  <  5. Dark-blue filled circles have a TS  >  25, the others are in the range 5  <  TS  ≤  25. In contrast to Fig. 3, the γ-ray emission was fitted by a single power-law component placed at the position of 3C 345. b) X-rays observed by Swift XRT between 0.3 and 10 keV. c) Optical (R-band) observations performed by GASP and SAO. d) Millimeter radio observations by the SMA at 230 GHz. The two orange downward arrows on top indicate the observation epoch for which a new feature was detected in the pc-scale radio jet of 3C 345, see Sect. 3.4 and Schinzel et al. (2010). Three dominant flare events of high significance observed on two-day time scales were labeled with I − III. Several weaker events were identified and labeled with numbers from 1 − 6.