Let’s start with the fact that we will choose a photo or image suitable for applying animation of falling snow on it.
Next, select the Brush tool. 
and open up the Brushes palette (F5). Select the Brush Tip Shape and apply the following settings.
Dynamics of the form:
Scattering:
Use the white color for the snow that we create on the new layer.
Create a copy of the snow layer and lift it up so that the bottom of the new snow layer touches the top of the original snow layer. Drain both snow layers – select them and press Ctrl + E.
Open the animation window. For the first slide, leave a drawing with a snow layer, like here.
Copy the existing slide (click on 
in the animation window) and smoothly lower the snow layer so that the top of the snow layer (which was outside the image) appears on the image.
Select both slides and click Tweens animation frames in the animation window.
Select these parameters in the Frames window that appears.
You will automatically get intermediate slides with the movement of snow.
Removing the last slide will fix the rotation of the animation of falling snow, making it continuous. Adjust the delay for the duration of each slide (set the duration of each slide under the slide), as shown below.
To save the animation go File – Save for web.
Choose the format of GIF and the number of colors 256.
Further, at your discretion, you can change the shape of the brush, the size and all that you want. With such wonderful Christmas animations, you can bestow your friends and loved ones.
