Yes, Feit Electric string lights are rated for outdoor use and wet locations. To use safely be sure and plug the string lights into a covered GFCI outlet.
They can also be used indoors.
Here's a video with more information on how to install string lights.
Covers and or String Light Shades
Note: Do not cover the product with cloth, paper or any material not part of the product when in use.
Outdoor Plug Operation Temperatures
Although the outdoor string light is wet rated, it can also withstand temperatures between 125F to -13F (51C to -25C). If the conditions in your area extend beyond the products operation temperatures, a slow start or even flashing would not be uncommon.