Slavoo as you know accuweather uses 3 kind of codes/ways to visualize the icons
viewtopic.php?f=10&t=4837
The best way to have more clear night icons is the tag for the 40 images.
THIS CANNOT BE CHANGED BECAUSE THESE ARE THE DEFAULT TAGS FROM ACCUWEATHER.COM..
So this does not depend on us. BUT you need to understand that depends a lot on the icons used!
The numbers that you ask for, have day and night images. Now there are conditions like fog, full cloudy, full rain, full snow, that have the same visualisation because in real life, the sky for these conditions are full of clouds without sun or moon.
Now there are many icon sets that have day/night images (except for the fog)
Example using the above weather set
7-Cloudy = 38-Night Mostly Cloudy
11-Fog
12- general showers
13- Mostly Cloudy with Showers = 39-Night Partly Cloudy with Showers
14- Partly Sunny with Showers = 40-Night Mostly Cloudy with Showers
18 - general rain
19 - general flurries
20-Mostly Cloudy with Flurries - 43--Night Mostly Cloudy with Flurries
22 - general snow
EXTRA
The "37" is not the fog for the night. This is the HAZE condition so it's the number "5" for the day.
5--Hazy Sunshine - 37--Night Hazy
CONCLUSION:
1. We can't do anything. The tags cannot be changed since are the ones that are provided from the accuweather.com service
2. As you can see, the answer to your question depends a lot on the icon set used for the widget. There are icon packs that have the same weather icons for some of the above numbers. So in this case depends on the user who created them.