In times of hot dry weather some cities ban the use of garden sprinklers why do you think there is such a rule

ban the use of garden sprinklers during hot dry weather because If water use doesn't decrease soon, pressure could start dropping and supplies could cut out without warning. Weeks of dry weather, high temperatures and warm winds have pushed water use almost to the limit.

To restrict the amount of water being utilized from a limited supply.

Explanation:

A sprinkler or a hosepipe ban gets imposed in certain cities during hot weather conditions in order to conserve the declining levels of drinking water, that is, stored in the reservoirs at the time of drought. Once the rainy season comes back the ban gets lifted as the reservoirs get filled once again, and it is more essential to provide water to the public, as the grass can always grow again.