What I mean is -- could there simply have been a lot more prostitutes about in the warmer summer months?
I suppose you should enlarge that question Charles to get some kind of semi accurate idea of what the correct answer is....both full time Prostitutes and Unfortunates solicited, the second group did so whenever did not find work and they desperately needed money for food or lodging. The first group did so daily, it was the only way they earned money.
The Canonicals seem to have a mix of both. We have evidence that Annie, Liz and Kate did other things to earn legitimate money...sewing, cleaning and sewing/knitting and hops picking.
The last job is the one that is sort of an answer to your question.....Kate Eddowes, and many other Unfortunates, preferred working outdoors picking hops in the summer months. Granted, these cases were all Fall murders, but Kate had only just returned to London in late September, so perhaps other street women were also returning later that Fall.
I think overall fewer women would be working the streets in summer, based on a decrease in Unfortunates being able to find seasonal work.