I also suspect it is due to temperature and humidity. After driving for a hlaf an hour or so the digits start fading back into view and eventually looks normal! I will have the cluster off tomorrow or next week and will keep you guys posted on any progress.
95 E320 Coupe Black - 70,000 miles with Parchment interior. Stock through out
93 400E Dark Blue - 65,000 miles Sold to my dad
86 300E Gold(yuck!!!) 126,000 miles- Sold, a really fun car with a lot of memories