Multiwavelength light curve of V339 Del during the outburst in August 2013. Top panel: optical observations in the V band obtained from the AAVSO-LCG⁴ service. Middle panel: the Fermi-LAT flux (filled symbols) and upper limits (empty symbols) above 100 MeV in one-day (circles, thin lines) or three-day (squares, thick lines) bins. A 95% C.L. flux upper limit is shown for time bins with TS < 4. Bottom panel: upper limit on the flux above 300 GeV observed with MAGIC telescopes. The grey band shows the observation nights with MAGIC. The dashed grey line shows a MAGIC observation night affected by bad weather.