  The hot gas in clusters of galaxies creates a distinctive spectral distortion
in the cosmic microwave background (CMB) via the Sunyaev-Zel'dovich (SZ)
effect. The spectral signature of the SZ can be used to measure the CMB
temperature at cluster redshift ($T_{\rm CMB}(z)$) and to constrain the
monopole of the y-type spectral distortion of the CMB spectrum. In this work,
we start showing the measurements of $T_{\rm CMB}(z)$ for a sample extracted
from the Second Catalog of galaxy clusters produced by Planck (PSZ2) and
containing 75 clusters selected from CHEX-MATE. Then we show the forecasts for
future CMB experiments about the constraints on the monopole of the y-type
spectral distortion of the CMB spectrum via the spectrum of the SZE.
