The ordinance is here: https://www.plano.gov/DocumentCenter/View/8782
Briefly, in the summer you must water from 6 pm to 10 am (my bad - not 9:00 am as I said); and in the winter you must water from 10 am to 6 pm (risk of freezing water on sidewalks).
The fine / administrative penalty, is $150, and they can also lock the sprinkler backflow preventer closed.
Sec. 21-60.1. Criminal Penalty
Any person, firm or corporation who violates any term or provision of this
Ordinance shall be deemed guilty of a misdemeanor and upon conviction thereof shall be
subject to a fine in accordance with Section 1-4(b) of the City Code of Ordinances for
each offense. These criminal penalties may be imposed in addition to any Administrative or
Civil Remedy listed herein. Each day a violation continues shall constitute a separate
offense. The requirement of a culpable mental state is expressly waived for criminal
These remedies are available if the city declares a drought condition; however Plano, TX is sitting at 48 inches of water for the year, and we still have watering restrictions.
Also, since this is Texas, the city always reserves the right to shoot you.