Freezing temps with rain barrels

I have been collecting rain water in rain barrels but some really cold temps are heading my way.  How much water do I drain out of my barrels to allow for the water expansion from freezing?  I don't want my barrels to split like the guy across the street.  I don't have any electrical near the barrels or I would use the wires that keep the eave troughs from freezing.  Any suggestions?  Had heavy rain last night and all the barrels, the overflow barrels are full.  I removed the downspouts out of the barrels around three AM.  My system was overflowing.  Thank God for my sump pumps and back flow.  Everything got a major workout.  This may be the only rain for the summer so I have water saved in anything that would hold water.   Thank you for any advice you may have.
Johanna

Where are you located?
I cannot imagine that on the northern hemisphere, now in May, there will be temperatures low enough to freeze a massive body of water like in a rain barrel.
We only empty our barrels in winter.

If the temperatures dip below freezing, it would take several days and nights considerably below freezing to turn all the water into ice.
You could get a thin crust of ice on top, but that should be it.

Huh. I have seen IBCs and barrels freeze solid several times, none have ruptured. All were open, generally they were effectively full if not overflowing, and the barrels mostly? all? had larger openings cut in them than the 2" bungs.

Min temps were probably about -10c.

I wonder what was different to make your neighbours blow out...

If your rain barrel has a valve at the bottom you can just wrap a rag around the valve area to keep it from freezing. One of our rain barrels has a hose on it and the valve is on the end of the hose. On that one I put the valve end of the hose up into the tank so it was down under the water which won't freeze solid unless the temps stay below freezing day and night for at least a week.  I don't bother if it's just an overnight frost, but we recently went through some 18*F nights where the daytime temps stayed in the upper 30's. Everything was fine after a few days of extra cold. We have a couple of barrels with open tops and no hose fitting at the bottom. Those we keep in the greenhouse and fill up in the fall. They are fine all winter, and we're in Minnesota.

Agree with the others.  If the daily high and daily low average out anywhere above 25 degrees, I think you're fine for a day.  If it's above 32 degrees you're good for a long time.  The biggest risk is the plumbing/piping where the thermal mass of the water can't help itself as much.

Hi I'm in zone 3 in Northern Alberta.  The Arctic low that has been over us most of the winter is back.  I guess I'll be ok.  Had snow yesterday and a cold night.  I removed a couple of inches of water from each barrel.  I put the excess water into containers in the garage.  I broke one of the handles on the bottom spout. it was warm again by lunch time so no harm.  If the temperature drops down to -30 C in under four hours with major winds the barrels get fragile and split.  Sometimes you don't know there is a rupture until the barrel defrosts.  I usually set up my barrels after the last snow fall usually the last weekend in June.  I have lots of plants in my raised beds.  The beds are 3 feet or more high.  I have sort of mini green houses on them to let me extend my short growing season.  Two weeks ago I shoveled snow onto the beds, Screwed on my "windows"(they are wooden frames with heavy plastic covering.  We get bad hail storms so glass simply will not last a season.)  The snow melted so I planted in my cold weather plant starts like leeks, mints, parsley, thyme, garlic and strawberries.  I have the warm weather starts like tomatoes, oregano, terragon, basils, etc. are still in their containers in a mini green house on another bed in case there is a serious cold snap.  This lets me bring them back inside but so far a hundred watt light bulb has kept them warm enough.  I'm making an other large raised bed with another mini green house so I can plant carrots, beets, and onions.  I use my barrels to water my garden.  My first year of gardening here I used over $200. water the first month.  I use some grey water, but I try not to use tap water.  

You have a technically interesting problem, coming from Australia I cannot comprehend tanks freezing!!
It is something I am interested to get a handle on.
For a start you IBC may be splitting because the plastic might be reacting to the cold and becoming brittle, the damage may not be the freezing water.

I am aware people have installed the water tank in a barn, and even had warmth generated to keep the barn above freezing.
I have had people in N.America install them in the basement as the house is being built.
I also wonder if you had a 20,000Litre tank if it may be too big to freeze.
In Australia I have 20,000Litre tanks and also a 190,000L tank.

Also, putting the tank partially underground will help, since the earth will have an insulating factor of some sort.
But you cannot go completely under because the soil may collapse an empty tank.
We do not generally get freezing where I live.

I found this on a web site in Australia of all places.
Stop tanks freezing

1. Use Larger Tanks
This is a straightforward one. A larger volume of water takes a longer time to freeze completely, compared to a smaller volume of water.
When the tank is refilled the new water is a little warmer than what is already in the tank and thus delays freezing further.
This cycle relies on regular water usage and replacement.
2. Use Round Shaped Tanks
For the same volume, round shaped tanks have a smaller surface area compared to rectangular or cube shaped tanks,
causing less heat loss and providing better insulation.
3. A Sloping Tank Cover Helps
Flat top tanks may have a gradual buildup of ice on top mostly due to water remaining from rains, reducing the temperature of the water
in the tank and increasing the chance of the water freezing. A sloping water tank cover or top prevents ice formation on the top and keeps the water tank a little warmer.
4. Ensure Proper Tank Insulation
Proper tank insulation is a must if you want to avoid freezing of the water during the winter.
A good insulating material covering the tank from the sides and the top will prevent heat from leaving the tank,
keeping it warm enough to avoid freezing. Many tank suppliers sell optional covers with their tanks.
5. Avoid Insulating the Bottom of the Tank
Although as mentioned above, tank insulation is important, it is a good idea to avoid insulating the bottom of the water tank as warmth from the soil below
increases the temperature of the tank and prevents the water in it from freezing.
6. Keep the Water Moving
Moving water is much less likely to freeze than standing water. In very cold conditions, if the water from the storage tank
is not going to be used for a few days, the tank water should “used” or moved around somehow to prevent freezing.

Thinking about IBC's, if you do not have the base of the actual tank on the ground that may hasten freezing.
But on course if the ground is frozen anyway, will that help?

Food for thought