PEWAUKEE, Wis. — Connie Watt, a former vice president at a home inspection company, sat at her kitchen table on Saturday morning and counted out nearly $20,000 in crumpled $1 bills, hastily signed checks, crisp $100 bills and loose change that schoolchildren had delivered to Pewaukee High School in plastic bags.

Ms. Watt, the mother of Houston Texans defensive end J. J. Watt, made sure the money was counted three times, with the help of a few volunteers, before it was added to the millions already raised by her son’s charity to help the victims of Hurricane Harvey in southeast Texas.

The drive started Aug. 27, when J. J. Watt posted a minute-long video to his Twitter account in which he told his four million followers, “It’s very tough to watch your city get hit by such a bad storm and not be able to help,” and asked fans to donate — any amount — through an online link.

Since the initial video was posted, it has been shared 16,000 times. Watt has since made a dozen more videos updating the drive’s success as its fund-raising (he initially set a target of $200,000) surged past one goal after another. On Sunday night, Watt announced that more than $18.5 million had been collected through the website youcaring.com.