One of the easiest ways to decide when is the right time to harvest, is to use the Vaakapesäseuranta (hive weight tracking) website. On these webpages it is possible to access data from several hives all over Finland that have been installed on electronic weighing devices in order to track daily changes in the weight of the hives. When the hive reaches its peak weight, it is usually time to start harvesting because the hives will start losing weight as the bees begin eating the honey reserves.
At the Inkoo hive which we have been following, the max weight of about 100 kgs was reached on 18th July and then 26 honey cakes were removed (click on the link above to see the data)..
This roughly coincides with the end of the maitohorsma flowering season. Some honey could still come from heathers which will start flowering soon, but I don't think we have large amounts of heather in this area. We noticed that some of the bees were carrying large amounts of bright yellow pollen which suggests they are reaching some rapeseed fields but these are really at the limit of their range and suggests they have been travelling much further in recent days.