The rain sound effect used in the song can be found here and allows for use as a sample as long as it isn't a reupload of just the sound itself.
You are free to copy, distribute and transmit this work under the following conditions:
*Please contact me if you would like to use this in a commercial project. We can discuss the details.
** Contains third-party samples.
Excercise caution when using it, refer to author comments / contact the author for details.