More information gained be gained quicker by simply observing the flight activity from hives than from weight data. In fact, I can always tell when the main flows hit by the flight activity and also the high aroma. But if you don't believe me:

For three consecutive years, the flight activity from 10 honeybee colonies was recorded for a whole
day at the beginning, middle and end of the flow. The outgoing flights started at about 9.00 h
reach a maximum between 14.00 and 16.00 h and ceased at about 21.00 h. Multiple correlation
coefficients of humidity, temperature, wind speed and light intensity with flight activity ranged from
+ 0.701 to + 0.978, all highly significant. Correlation coefficients of temperature with flight
activity ranged from + 0.532 to + 0.947, also highly significant. There was a significant direct
relationship between flight activity and colony weight gain 30 min later. This weight gain was
correlated with honeybee activity and the above four weather factors ( + 0.490 to + 0.837, all
highly significant). The mean daily flight activity of a colony was highly significantly correlated with
the total weight gain of the colony at the end of the season (- 0.766 to + 0.879). This relationship
was not significant on a day with no weight gain. Mean flight activity significantly differed between
years. Overwintered colonies flew more than package colonies. A single day's activity was related
to the total seasonal weight gain of the same colonies. The results suggested that a single day's gain
is also related to the total seasonal gain, and that by weighing colonies on two consecutive mornings
the highest-gaining colonies could be selected for breeding.

Szabo, T. I. (1980). Effect of weather factors on honeybee flight activity and colony weight gain. Journal of Apicultural Research, 19(3), 164-171.

see also
http://www.keltronixinc.com/?v=7516fd43adaa

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