It's dry a lot of the time: for 88% of all 10-min periods and 81% of all 1-hour periods. Although the statistics for 24-hours looks less good - only 37% of days are completely dry.
My bike-ride to work is 5 minutes each way. So there's an 88% chance of being dry each day when I go to work - i.e. it'll rain on me on about only 2-3 days per month.
I also looked at Helsinki (Vantaa) airport 1985-2015 for a few more things PER YEAR:
- 52 BBQ days (Tmax>18C, sun>4hrs, rain=0)
- 17 hot days (Tmax>25C)
- 85 gloomy days (sun=0, rain>0)
- 70 cold days (Tmax<0)
Data from Finnish Meteorological Institute