Don't be fooled too badly by a little warmer weather. The ice will actually grow fatter with temps around 35-40 during the day and below freezing during the night. This allows the water to flow a little more and continue the freeze cycle during the night.
Also, take into consideration the direction the falls face. Hidden falls faces almost directly north and even if it is 40 degrees during the day, that little grotto canyon rarely gets above 20 and NEVER has any sun on it.
I've seen some of the very large falls in Canada actually double in size within a week or two a good freeze cycle of warmer days and cold nights, and actually shrink back during extended extreme cold spells.