apt repository for weeWX

Tell the system to trust weewx.com

curl -s http://weewx.com/keys.html | sudo apt-key add -

Configure apt

For python3 (debian10 and later): 
curl -s http://weewx.com/apt/weewx-python3.list | sudo tee /etc/apt/sources.list.d/weewx.list
For python2 (debian9 and earlier): 
curl -s http://weewx.com/apt/weewx-python2.list | sudo tee /etc/apt/sources.list.d/weewx.list

Install and/or Upgrade weeWX

sudo apt-get update
sudo apt-get install weewx