Alex made landfall June 30 in northern Mexico. Associated strong winds and heavy rain led to flooding in parts of south Texas.
The designation makes federal funding available to affected people in Cameron, Hidalgo, Jim Hogg, Maverick, Starr, Val Verde, Webb and Zapata counties.
Federal help is also available, for government and nonprofit groups, to repair or replace damaged facilities in Cameron, Hidalgo, Jim Hogg, Jim Wells, Maverick, Starr, Webb, Willacy and Zapata counties.
Gov. Rick Perry last week sought the federal disaster assistance.