In an urbanized area most "is it going to rain?" questions are short-term, e.g. is now or 30 minutes later a good time to bike home?
Perhaps this wouldn't be as useful in other areas. The Netherlands gets very spotty rain. So even if you've got a 100% chance today it's probably 1-2 hours spread throughout the day, and sometimes very heavy rain followed by a dry spell.
The only time I've seen it to be incorrect is if a moving rain cloud just barely misses you due to changes in wind patterns.