STANDARDS SECTION XVIII - TOURNAMENT STANDARDS OF PERFORMANCE b.  Procedures for Measuring/Monitoring Weather Conditions i.  One-half hour before match play begins; ii.  Middle of the scheduled day; and iii.  Just prior to beginning of the last match of the day, or prior to the  start of the first evening match. iv.  Following any suspension of play; and v. At the discretion of the Supervisor, in consultation with the  Tournament Physician and/or PHCP. d.  Modification of Play Procedures, Singles c.  Modification of Play Timing and Weather Condition Change The WBGT Index or Apparent Temperature should be measured by the PHCP  a minimum of three (3) times, and a maximum of five (5) times, per day. The  readings will be determined by the PHCP and the Supervisor prior to the start  of play and will be posted in the Supervisor’s office. Measurements should  be taken every two (2) hours, but at a minimum, three (3) readings should be  taken at the following times: The WBGT Index or Apparent Temperature also should be measured  under the following circumstances: When the Extreme Weather Condition Modification of Play is in effect  before the start of a match, the procedures set out below in sub-Section  d, shall be followed. In the event that during the day there is a change in weather conditions as  determined by this periodic monitoring, the Extreme Weather Condition  Rule can be put into effect at any time on all courts, including matches  already in progress. Once notified that the Extreme Weather Condition  Rule is in effect, the Chair Umpire must inform the players at the next  opportunity, no later than the next change of ends. If there is a sudden change in weather conditions and the Rule is lifted,  those matches already in progress will continue under the Extreme  Weather Condition Rule. In the case of rain or interruption to play, the  Supervisor and PHCP can re-assess the Extreme Weather Condition Rule. A 10-minute break will be allowed between the second and third sets  365