I was curious at what speed the winds have to reach before emergency officials close the bridges in Nassau County.

Here it the answer I received from Nassau County Emergency Management:

Bridges are closed once tropical storm force winds (TSFW) are reached. TSFW are considered to be 39 MPH sustained. The way sustained winds are determined is by taking a one minute average wind speed reading.

Nassau EM remotely monitors wind speeds on the Thomas Shave Bridge. Once winds approach TSFW, they will be confirmed by personnel on the ground.

The best way to be kept in the loop and be notified of a bridge closure is to register for Citizen Alerts through the Nassau EM webpage or look for updates on their facebook page.