  We report the results of six years (2013-2018) of measurements of $^{222}$Rn
air concentration, relative humidity, atmospheric pressure and temperature in
the halls A, B and C of the Canfranc Underground Laboratory (LSC). We have
calculated all the Pearson correlation coefficients among these parameters and
we have found a positive correlation between the $^{222}$Rn concentration and
the relative humidity. Both correlated variables show a seasonal periodicity.
The joint analysis of laboratory data and four years (2015-2018) of the
meteorological variables outside the laboratory shows the correlation between
the $^{222}$Rn concentration and the outside temperature. The collected
information stresses the relevance of designing good Rn-mitigation strategies
in current and future experiments at LSC; in particular, we have checked for
two years (2017-2018) the good performance of the mitigation procedure of the
ANAIS--112 experiment. Finally, in another measurement (2019-2021) for two
years of live time, we report an upper limit to the residual $^{222}$Rn content
of the radon-free air provided by the radon abatement system installed in the
laboratory.
