Arriving with distinct ringtones and vibrations, the wireless alerts resemble text messages when they pop up on cellphone screens, but they rely on different technology. All wireless carriers participate in the system, and Hawaii’s emergency agency is among hundreds of federal, state, local, tribal and territorial authorities with the power to use them, according to FEMA.

There are three types of wireless alerts: those issued by the president; those involving imminent threats to safety or life; and Amber Alerts for missing children. More than 30,000 alerts have been sent since the system’s introduction, according to the communications commission. In 2016, law enforcement officials in New York used the system to circulate a kind of digital wanted poster in hunting for a man wanted in bombings in Manhattan and New Jersey. The alerts are free; consumers can use their phone settings to opt out of getting all but those sent by the president.

The system has come under growing scrutiny in recent months, with public safety officials complaining that it requires upgrades on several fronts. Critics say alerts are often sent too widely, sowing fear among people unlikely to be affected by the threat in question. There have also been calls for the alerts to be sent in languages other than English. The communications commission has approved some changes, but they will not take effect until next year.

Last month, officials from Harris County, Tex., met with commission officials about their frustration over how, during Hurricane Harvey, they could not pinpoint alerts to area residents most likely to be affected by the storm without alarming a broader swath of the county.

The commission, which sets the technical standards for the alerts, is under pressure to update its rules to force wireless carriers and phone makers to work together to ensure that the system is more effective. Last week, Mr. Pai announced a proposal to update the alert system to improve its location-targeting ability.