Spectral evolution of the persistent emission of SGR 1935+2154 observed with NICER after the initial observation obtained on 2020 April 28. From top to bottom, the panels show the evolution in the 0.3–10 keV range of the unabsorbed flux (in units of erg s⁻¹ cm⁻²), the BB temperature, and the emitting radius assuming a distance of 9 kpc. In all panels, green dashed lines show the average of the values inferred from historical NICER observations obtained in 2017–2019, before the source burst active period. The blue vertical dashed, dotted, and dashed–dotted lines, respectively, mark the times of the FRB-like event, two additional weak radio bursts (Kirsten et al. 2020), and another weak radio burst reported by FAST (Zhang et al. 2020) from the source. The red solid curves in the top two panels constitute the best-fit double exponential decay models to the flux and BB temperature, displaying an initial very rapid rise and then a much slower decline.