Synonyms for Severity (same or very similar meaning)
WordNet sense 1 (used of the degree of something undesirable e.g. pain or weather):
badness, severenessWordNet sense 2 (something hard to endure):
asperity, grimness, hardship, rigor, rigorousness, rigour, rigourousnessWordNet sense 3 (extreme plainness):
austerenessWordNet sense 4 (excessive sternness):
hardness, harshness, inclemency, stiffnessFrom the ODE community, based on WordNetadd/edit