Drizzle falling from blackberry vines

I recently saw something I don't understand.  I was standing next to a blackberry vine looking up on a hot sunny day with a dark evergreen tree in the background and saw some very small droplets of moisture springing up from the tops of the leaves a few inches and falling down.  A steady drizzle of them.  How/why would a plant do that?
The vine is growing and fruiting well.  There was nothing coming down from above the vine and no breeze.  I tried to take a video with my phone but the droplets were so fine they did not record well.  I'll try to get that posted later.

There can be several reasons for this. This time of year, the plants will utilize different ways to conserve water. Some will store water between leaves and it can also be part of condensation from temperature fluctuations. If you have high humidity, and have places of shade, hot air will enter the shade and condensate the water on the underside of the leaves. I see this happen in my garden, since we have a large pecan tree which gives a lot of shade. Underneath it, I grow currants, strawberries and mushrooms. We also have drip irrigation installed, which is underneath mulch. There is a temperature difference of 5 to 15 degrees during the summer, when the leaves are dense. Note that we live in SoCal grow zone 10b, so it gets very hot here.
One of the things I am working on, is getting enough tall trees to lower the temperatures and increase humidity in our forest garden. We have a partly mediterranean and desert climate here, and I want to change it toward a more subtropical climate. That will be possible with enough tree coverage.
Anyway, that’s my 2 cents.

I checked and the temperature at the time was 92F and humidity was 42%.  The sky was clear and the sun shining on the top surface of the leaves where the droplets were coming from and so I don't think it was some sort of condensation.  My difficult to see video is linked below.  In the first few seconds of the video look at the evergreen tree in the background to see the tiny light specks falling down.  These were springing up from the top surface of the leaves with enough velocity to travel up several inches then arc over and fall.  
https://www.facebook.com/share/v/1CtmKGyGYJ/

Then I am not sure. Did you make sure it’s water? I can see what you mean, when I see the video. It looks like it’s coming from the tree.

The tree is about 40 feet away and there was no wind.  I also looked to see if they were coming from above and just bouncing off the leaves, maybe coming from the evergreen or the cottonwood, but I couldn't see anything coming down from above.  If I see it again maybe I'll get a ladder out so I can get closer to the leaves to be sure they are not falling out of the sky.  The droplets were so small I didn't even feel them when they landed on my hand.  I suppose they could be solid like maybe pollen or spores but would have to be about as dense as water to fall that quickly.  Pollen counts have been low lately but the sword ferns are producing clouds of spores, maybe those are big enough to see.  I guess I could  put a glass slide out to collect some.  

Maybe it was Honeydew: This is a sugary liquid excreted by sap-sucking insects like aphids, scale insects, and others feeding on a tree's internal fluids.

What time of day was it?

How moist was the soil?

It sounds like guttation fluid to me

It was about 3:30PM so near the day's peak temp.  The irrigation system was scheduled to run that evening and has automatic ET adjustment.  I haven't check soil moisture with a meter in several weeks but it should be in a normal range.  

Thanks for the inputs that helped me narrow the cause of what I was seeing enough to ask a local Master Gardener and get the following reply:

"The described raining droplets from blackberry leaves in sun are most likely a classic case of guttation, not a sign of disease or pest, and are normal for a well-watered, vigorous plant, especially under fluctuating temps and humidity. Just monitor for overall plant health and don’t worry unless additional stress symptoms appear.  

What Causes Guttation?    
Guttation occurs when plants expel excess water through specialized structures called hydathodes, typically at the leaf margins or tips, but can also occur on other parts of the leaf surface. This process is driven by root pressure, which develops when soil moisture is high (such as with diligent irrigation), the air is humid, and transpiration is relatively low (often overnight or early morning but can also occur with rapid temperature/humidity changes). In some cases, the droplets are seen “springing” due to the force of expulsion and local microclimate effects on the leaf surface.
 
Why the Droplets Spring or Arc    
While guttation usually presents as droplets forming at the leaf edge or tip, in some plants or under strong root pressure (which is likely during heavy irrigation and hot, sunny conditions), droplets can be forcefully ejected, creating an arcing effect as described. Since the plant is well-watered and temperatures fluctuate, water uptake at the root may exceed what the plant can release by transpiration alone, so guttation pressure pushes droplets visibly outward.  
 
Is This a Problem?    
Guttation is generally not harmful and does not indicate disease or pest infestation. It simply means the plant is taking up more water than is leaving via stomata. However, if guttation is extremely frequent or copious, it can indicate overwatering, and long-term, excess mineral residue from the droplets (especially if using hard water or fertilizer) may slightly irritate delicate leaf tissue. Additionally, on rare occasions, guttation droplets can harbor bacteria or fungal spores; if these are reabsorbed, leaf spots can develop, but this is uncommon.
 
What to Do  
• No action is usually needed if the plant appears otherwise healthy and is fruiting well.
• Maintain good soil drainage and monitor irrigation, especially in high temperatures.
• If large amounts of guttation persist, consider reducing watering frequency slightly and check for sticky, white, or crusty residues on leaves (this indicates mineral accumulation)."

I guess I hadn't noticed this before because the droplets are so fine and difficult to see and so probably do happen on other plants.  At least I know these plants are getting plenty of water.