In the last few decades, extreme weather events mostly characterized by more intense and frequent precipitation and wind incidents have risen, and current climatic projections strongly suggest that this trend will keep its pace in the future. These climatic conditions pose additional hygrothermal loading onto the built environment, which may lead to moisture induced deterioration and even strength reduction in masonry. Despite their already long service lives, this impact may in time become problematic for historic buildings, which, by nature of their design and construction, interact with moisture and climate to a far greater degree than modern buildings. The PARNASSUS project was set up with the aim of identifying and quantifying the impact of environment on historic buildings in the face of a changing climate. As part of this project, an extensive environmental monitoring campaign was carried out between 2012 and 2014 at Blicking Hall, a National Trust property in Norfolk, England, with the aim of providing further insight into the building's overall performance under hygrothermal loading. Environmental monitoring work targeted not only indoor and outdoor conditions, but provided information about the temperature and relative humidity profiles across the walls by means of in-wall probes. Wind and rain gauges helped quantify other environmental parameters. This paper presents the findings from this environmental monitoring work, with specific emphasis on the basement suffering from sustained saturation in vapour phase and resulting biological growth, as well as the Long Gallery, where Blickling's valuable library is kept.