Tea preparation styles vary according to the season: Furo Temae style for summer and Ro Temae style for winter.
The main difference between preparing tea in summer and winter is that in summer the Kama/kettle is placed on a brazier and in winter the Kama/ kettle is placed in a sunken hearth or Ro/a square hole in the Tatami flooring. According to this the utensils used are placed at slighly different.
Also the Sumi-demae /charcoal procedure is different in each season.
Furo Temae style (from May) Ro Temae style