The Rain Bar is a J. W. Lees pub on the west side of Bridgewater Street across from the Pevril of the Peaks.  It sits close to the point where the Salford and Manchester Junction Canal joins the Rochdale Canal.  Lees web site says that the building was originally an umbrella factory hence, presumably, the name.

Today the Rain Bar building stands detached from its neighbours but that wasn't always the case, as you can see in the aerial photograph below, dated 1953.  The arrow points to today's building but it was then part of a triangular complex of buildings on this junction of the two canals.

My version of a map from the 1880's shows this in more detail and this speaks to the idea that it was a former umbrella factory.  The map indicated that number 80 Great Bridgewater Street was home to a silk and general warehouse.  The Kelly's Directory for Manchester and Salford, dated 1927, listed the occupant of number 80 as "H. T. Gaddum & Co, silk, spun silk, artificial silk merchants and shippers."  Prior to that in the 1860s the Slater's Directory listed a number of businesses operating in the building including:  Thomas Worthington's Girth & Brace Manufactury and Upholstery and Trimming Manufactury, and W. Crighton & Co Millwrights.  You will note from the map that there was indeed an umbrella factory in the area but it was across the canal in the Havelock Mill.  I am not claiming that number 80 was never an umbrella factory.  It may have become that after 1927, but I can find no evidence of it being used in that way.

The 1849 map (below) of the site shows that the area between number 80 and the canal, that was empty in the map above, was occupied by an Iron Foundry.  The 1863 Slater's Directory of Manchester and Salford confirms this by listing "William Crighton's & Co - Iron Founders and Millwrights" at this address.  Today this area provides a patio for the pub.  The red arrow points to the location of the Rain Bar building.