The rules of cricket
Law 11 (Covering the pitch)
1. Before the match
The use of covers before the match is the responsibility of the Ground Authority and may include full covering if required. However, the Ground Authority shall grant suitable facility to the captains to inspect the pitch before the nomination of their players and to the umpires to discharge their duties as laid down in Laws 3 (The umpires), 7 (The pitch), 8 (The wickets), 9 (The bowling, popping and return creases) and 10 (Preparation and maintenance of the playing area).
2. During the match
The pitch shall not be completely covered during the match unless provided otherwise by regulations or by agreement before the toss.
3. Covering bowlers' run ups
Whenever possible, the bowlers' run ups shall be covered in inclement weather, in order to keep them dry. Unless there is agreement for full covering under 2 above the covers so used shall not extend further than 5ft/1.52m in front of each popping crease.
4. Removal of covers
(a) If after the toss the pitch is covered overnight, the covers shall be removed in the morning at the earliest possible moment on each day that play is expected to take place.
(b) If covers are used during the day as protection from inclement weather, or if inclement weather delays the removal of overnight covers, they shall be removed promptly as soon as conditions allow.