  Charge density waves are a common occurrence in all families of high critical
temperature superconducting cuprates. Although consistently observed in the
underdoped region of the phase diagram and at relatively low temperatures, it
is still unclear to what extent they influence the unusual properties of these
systems. Using resonant x-ray scattering we carefully determined the
temperature dependence of charge density modulations in
(Y,Nd)Ba$_2$Cu$_3$O$_{7-{\delta}}$ for three doping levels. We discovered
short-range dynamical charge density fluctuations besides the previously known
quasi-critical charge density waves. They persist up to well above the
pseudogap temperature T*, are characterized by energies of few meV and pervade
a large area of the phase diagram, so that they can play a key role in shaping
the peculiar normal-state properties of cuprates.
