First time load glitch

[shackbill]

I have a web page that displays snow but the first time the page is loaded the display is not right. But after page refresh all works fine. anyone have this problem or idea why it is occurring. You can see screen video here
https://publicshack.s3.us-west-2.amazonaws.com/particleGlitch.mp4

or visit the page here:
https://pos.santaskottage.com/