Weather from the Bee's Perspective

Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. (Webster Dictionary)

Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. (American Meteorological Society)

A microclimate is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. (Wikipedia)

Visualizing Weather From a Bee’s Perspective

Bees have very distinct weather related behaviours that we can use to convert data into visual tools that beekeepers can use to help them better understand their environment and potential challenges

Over the last year I have developed a simple approach using temperature , wind and rain data to visualize and quantify 2 phases of foraging, typical clustering, brood rearing and queen rearing. The use of solar radiation would also be very useful to account for cloud cover.

The results can be used to modify hive management approaches (e.g. timing of activities), measure the cold intensity over time to help find better wintering approaches and stores requirements

This data along with other field measurements such as continuous hive weight monitoring, internal hive readings temperature/humidity and actual hive inspections allows us to increase our overall understanding of our “local” environment


Reference: BC Beekeeping Bulleting #111 - Bee Behaviour During Foraging

Here is weather filtered through some bee behaviours.

Bees start actively foraging at +8C (46F) (Pollen)

FDH 8 - Forage degree hours >8C / 46F

Some nectars only flow at higher temps (Clovers) – best from 16C to 30C (61F to 86F)

NDH 16 - Nectar degree hours >16C / 61F

Forage Hours (add all daily hours where temperature was above 8C with daylight)

Bees start to cluster or are hive bound below 8C / 46F

CDH 8 - Cluster degree hours <8C / 46F (Energy Requirements/Cleansing Flights)

Cumulative CDH 8 is used to measure overall progression of winter over time

Hard to collect nectar and pollen when raining (Flag days with precipitation)

Plants need rain to produce good nectar/pollen (Daily RH% Lows)

Bees will stop foraging in winds above 40km/h (25mph) (Use hourly wind data)

Experience tells me very poor above 20km/h (13mph) especially if cooler.

Brood rearing occurs in the 35C / 95F sweet spot BDH 35 measure degree hours between outside temps and 35C (Energy Requirements)

Queen Rearing typically requires warmer days >20C with light winds QRH 20 measures degrees and actual available hours for each day where these conditions are met.

FDH (Forage Deg Hrs) =IF((Thr- 8)<0,0, Thr- 8))

Forage Degree Hrs measures the cumulative intensity (degrees) over time (daily sum) throughout the season when temperature are above typical temperatures 8C/46F when bees will be out foraging pollen, nectar and propolis.

NDH (Nectar Deg Hrs) =IF((Thr- 16)<0,0, Thr- 16))

Nectar Degree Hrs measures the cumulative intensity (degrees) over time (daily sum) throughout the season when temperature are above typical temperatures when bees will be out foraging nectar sources (many flowers will start releasing nectar above 16C/61F).

CDH (Cluster Deg Hrs) =IF((Thr- 8)>0,0, ABS(Thr- 8))

Cluster Degree Hrs measure the cumulative intensity (degrees) over time throughout the season when temperatures are below typical temperatures when bees are clustered. The factor can then be used to calculate energy requirements based on the various hive wintering methods (supplemental heating, wraps, venting, etc...)

Reading the Charts


A -30C day (24hrs)

CDH 8 =abs(-30-8) x 24hrs

CDH 8 = 912 deg hrs (Grey)

A 20C day (24hrs)

FDH 8 = (20 – 8) x 24hrs

FDH 8 = 288 deg hrs (BLUE)

NDH 16 = (20 – 16 ) x 24hrs

NDH 16 = 96 deg hrs (Orange)

Things you should look for:

1st Cleansing Flight of the season

Start of foraging season FDH 8/NDH 16

Do the corresponding hotspots match known nectar flows

When does my queen laying slowdown? When are your winter bees being raised?

Fall weather – Are you waiting too late to start your preparations?

Winter weather – Have I lost hives to starvation in the past? Are my hives insulated adequately?

Compare your location with where you get “online advice”

Should I be keeping bees in my area? Is it sustainable?

Below is an example of 3 years of hourly weather data put through my Bee Weather Analysis Tool. Notice the lack of the typical summer heating events. 2020 was a very tough summer on my colonies. It required me to monitor pollen levels (great quantities early in the summer season but very poor mid to late summer as the common forage sources require additional heat and solar energy (very overcast summer) that never materialized. Several of my colonies experienced very early brood shut downs that put the raising of winter bees at risk.

Hive Monitoring Data for the 2020 season in three different location.

Carcross is located next to several very large lakes that provide much longer frost free protection. It has more rain and things just grow better. It has natural pollen sources well into September.

Lewes Lake is an intermediate location with several small water bodies, large meadows (natural/mixed hay) and large south facing slopes (native grasses and vegetation). Natural pollen is available into early September.

Mt Lorne (Home Location) is what we would call native boreal forest with the odd small native meadow. The only disturbed soil is along the roads and at the widely distributed rural properties. There are no sources of non-native plants. Fireweed is typically that last significant source of pollen and nectar. We typically get our 1st major frost early to mid-August. I have developed my management activities to mitigated the lack of forage. Bee have been observed foraging significant amounts of plant rust spores (Fireweed/Willow/Rose Bush). During warm summers we will get very decent honeydew flows (spruce, deciduous tree/plants) .

Refer to Forage Page for more information.

Understanding your Nectar Flows Vs Weather

Source: Environmental Influences on Nectar Secretion, Leslie A. Kenoyer,


1. By increasing humidity, the secretion of water, but not that of sugar, from nectaries is increased.

2. Excessive water supply lessens the sugar surplus in the parts of the flower.

3. Dilution and washing by rain causes much of the sugar of nectar to be lost.

4. Rate of secretion for both sugar and water increases with temperature up to a certain optimum.

5. Accumulation of sugar in the flower and its vicinity varies inversely as the temperature.

6. The optimum condition for sugar secretion is an alternation of low and high temperatures.

7. Variation of atmospheric pressure has no marked influence on secretion.

8. Sugar excretion is markedly diminished in darkness on account of limitation of the food reserves of the plant. Water excretion may or may not continue, depending on the species. Removal of the leaves has the same deterrent effect.

9. The more favorable all conditions for growth and the more vigorous the plant, the greater is the amount of sugar secreted.

10. Nectar is most abundant early in the blooming season, other things being equal.

11. Accumulation and secretion of sugar is most pronounced near the time of the opening of the flower.