According to CBS, the snowstorm we see in this episode was real. As they stated on their website "5 Best Places In NYC For 'Elementary' Fans", as they were filming the episode "the weather goes from bad to worse". Instead of shutting the production down until it passed, dialog was changed/added to help explain their situation.
Mrs Hudson, the house guest in this episode is a nod to Mrs Hudson, the housekeeper at 221b Baker Street, where Holmes and Watson live in the original Holmes books.
Sherlock tells Watson Detective Bell once confided that he played Sky Masterson in his high school production of Guys and Dolls. In real life Jon Michael Hill who plays Detective Bell played Sky Masterson in high school.
Sherlock calls the storm 'the storm of the century'. Becky Ann Baker (Pam the snow plow driver) starred in a 1999 Stephen King made-for-TV movie called 'Storm Of The Century' about citizens of a Maine island trapped during a blizzard with a powerful supernatural being.