Wifi operates in either the 2.4Ghz or 5Ghz spectrum.
Your home router puts out somewhere between 100 mW (milliwats, or 20dBm) to 400 mW.
Water “resonates” at 2.45Ghz. (more accurately, the too-heavy-on-one-side water molecule will respond and change position when you alternate the field)
The average home microwave operates at 2.45Ghz centered, but will waffle down to around 2.3Ghz or so (they’re not super accurate, and do not need to be).
The average home microwave puts out around 1000 W (Watts).
There’s no such thing as perfect shielding; 1-2 W escapes from your microwave.
From this perspective alone, you get more 2.4Ghz radiation when you microwave a cup of tea in the morning, than you would ever get from your Wifi router all day.
From this perspective alone, if you stand in view of a gigantic fusion reactor for a few minutes, you’ll get more 2.4 Ghz radiation than your router would likely provide you in your entire life. We call this state ‘daytime’ and ‘going outside’.