In the northern hemisphere some people throw parties during July that mimic Christmas celebrations, bringing the atmosphere of Christmas but with warmer temperatures. Parties may include Santa Claus, ice cream and other cold foods, and gifts.
In the southern hemisphere, where July falls in winter, Christmas in July events sometimes have a winter Christmas theme. These may be a standard Christmas style celebration, held at a cold time of year, as Christmas is in the northern hemisphere.
In some western countries, July has a minor number of marketing opportunities. In the United States and Canada, there are no national holidays between the first week of July (Canada Day on July 1 in Canada and the Fourth of July in the United States leaving two months with no holidays. The late July period provides relatively few opportunities for merchandising so to justify sales shops sometimes announce a "Christmas in July" sale. I believe that Etsy does promote this "holiday" with special tags and merchandising opportunities.
Hope that helps...