The forecast was changed unexpectedly from low tonight of -20C (-4F) to low of -24C (-11F) outside temperature. It has been -21C (-6F) outside for the last hour and going down. I had one heater inside the garage before and added another one but temperatures inside the garage dropped to -4.5C (24F) and now the circuit breaker is tripping periodically. If the circuit breaker does not trip, I believe it may not go down below -7C (20F) inside the garage. But if the circuit breaker trips while I am asleep it can go below -10C (14F) inside the garage. I will stay up until it reaches and stabilize at the lowest forecasted outside temp of  -11F. Hoping the circuit breaker will not trip after that.
All my fig plants in the garage are in 5 gallon pots. I will not know until May-June which one did not make it. The breba will be gone anyway.
(It is already -22C outside. I should have hot tea now to stay awake in order to expect some figs coming summer)!!

Man, that's cold.  How many trees are at risk?

Use an extension cord from another part of the house to power the second heater.  Or crack the door a little bit.

In my house the power cord fits under the door.  If it's a long way use a thick power cord (14 guage or better) to the garage door and a flat cord for the last few feet.  You could also put christmas lights around your pots & plants - even cover them with blankets or tarps.  Put incandescant lights all around.  Don't start a fire, though! 

About seventy plus trees tangled into each other.....

Dang!!!

Hope for the best and if there on cement floor it helps a great deal as that helps keep the root zone at a more steady cold dormant temp warmer than the air temp insulated by the ground beneath that cement floor.

I have had  various size pots seemingly freeze at temps @ 6 to 8 degree's in my garage years back when we had near record cold outdoors at 23 below zero 1 night and 18 below zero the following night that whole week the high was 3 above zero during the daytime without windchill being factored in.

The only 5 gallon pot i had was my Violet de Bordeaux the rest 10g and above.
I kicked a 25 gallon pot like a man kicking a tire and that pot cracked i recall.
Sleep well what will happen will happen.
Best to you.

Here is the one and only time i took picture of thermometer in my garage at 12F
Best to you Akram.

You need a dedicated circuit breaker with at least 20amps for a portable electric heater. If you want to go the extra step wire 220v with 30 amp and get an electric heater with a blower. (I'm also and electrician).
Temperatures dropping below 20F is very damaging for tropical trees.

My grandfather used to keep four or five 55 gallon drums of water in his garage, and greenhouse to stablize temps.
A space heater pointed at the metal drums would keep the water warm along with the air,
if there was a power outage the water in the drums kept temps from plummeting until the power came back on many times.
He said he could at least get a few hours nap at night knowing the drums were there. 

I had it go down to 3 degrees last year, my first year black maderia survived with no problems (I hope it does again)  The only trees that died were drc-291 and I don't know why or if they were just that much more susceptible of the cold.  

I think that the wind is a huge factor too, I have a VdB Air layer in the garage straight from the basement and last night it got down to about -5 F with no frost biten leaves even.

Throw some blankets/tarps over them. It works well as a heat trap. Did that when my plants were outside and we were hit with artic outflows for 5 days. I went under the tarp to test temp. -- it was warm. Windchill was at least -15C

Ditto what Paul said. Also you can wrap the pots (individual or all- gathered close together), with Fiberglass insulation. Then cover them all with blankets and tarps, like what Paul mentioned.

Navid.

Forecast is so unpredictable tonight here.
The forecast was change to

Lo Tonight -24°C


But the actual at this time is:
 

 -25<sup>°C 

 
As Rcntor uggested, I used extension from another part of the house but the auxiliary heater tripped that circuit too which meant it was defective heater probably causing surge. Instead I added two lamps with 100W bulbs each. So, now the first heater added by two 100W bulbs is keeping the garage at 26F. I believe the worse is over now by 2:12 am, so time  to sleep and hopefully the figs will survive.
Tomorrow will be the day for better temporary arrangements because the highest tomorrow is -16C.
Thanks for all suggestion. Garage needs insulation too.</sup>

Dan's thought of water drums is a very good one, the thermal mass of one or two is amazing as a over night radiator of heat.  I use one with a farm watering basin heater in it, low wattage but always on and keeps the water warm enough to keep the workshop above freezing.  Same concept that is used in passive solar ( minus the farm heater!)

http://www.builditsolar.com/Projects/SpaceHeating/AWaterWallIntro.pdf

If your car fits in the garage now just warm it up and park it in there. Thats how I do it. Its my wives garage so there must be room for her jeep.

Ottawan,
I keep all my fig trees in unheated detached garage ,cover my trees
with plastic and old blankets and never lost a fig tree to the cold weather.
The winter temperatures here in Rocheste ny are very similiar to your,your fig
trees will be fine.Ciao,
Giuseppe

Thanks again for all the suggestions. I hope next time I will be ready.
Last night the lowest outside temp was -25C (-13F). I was able to maintain the temperature in the garage between 25F and 26E and that seems OK.
I guess the figs will feel tasty this year.

Even with the -16 last year I had brebas on my trees, young trees too.  The problem was the spring wasn't very favourable for the brebas to form and they got a light frost one night and fell off so there is still hope.

Ottawan - Hopefully there is a light at the end of the tunnel....weekend temps are looking up a little.

Chivas - Agreed, last spring was brutal.  Those few late frosts destroyed my apple blossoms.  I had five apples total, from 3 trees!  I hadn't taken up figs yet so I didn't have that issue.  Hopefully we don't see a repeat this year!

Dave
Actually most fruit crops last year were destroyed by unseasonably warm week in March that fooled the fruit trees. This warm spell was followed by temperatures as low as -10C a few times. This killed fruit buds in large areas around the great lakes.
I had only one peach on my two trees. No apples or apricots.

Hi Ottawan,
If your garage is attached  then I'd have the pots touching your house wall and create a room within a room with blankets, barrels of warm water etc + stop as much air infiltration as possible using whatever suitable means possible + using the good ideas from above as well! Those ext cords can melt so be careful not to overload the wires!

Ivan
That is my plan (for sure) for next year. It was my plan for 2012 also but the winter just came too fast here. I plan to use silver coloured bubble (insulation) sheets as wall like curtain to isolate a big part of the garage for figs. Too late this year. We are already in the deep freeze months (Jan and Feb).

I use incandescent bulbs too.  Put the lamps fairly close to where the figs are (those automotive trouble lights are easy to place).  

I like the water idea too, but I don't do that (no room for a 55g drum).  Thinking about one of those oil-filled portable radiator-style heaters (the electric ones) as an addition.  The oil is a heat sink too.

Mike

Akram my figs are in my shed unheated and no insulation last year seen temps in there -17 celcius my figs were fine even the ones in 1g pots. Like I mentioned to you before I dont water my figs from Late nov until early march.

Good Luck

That is re-assuring, Nelson.
And your showing here on the Forum is more re-assuring. Good to hear from you.

Hey Akram I wouldn't worry too much fig trees are allot tougher than I ever imagined and most of the varieties we grow can handle -10c and colder for a couple days with no issues.

The Main problem if its too cold for too long is they will generally take longer to break dormancy and hence possibly fruit too late but I dont think you will have that problem.

My dad's figs also in his garage its not attached to the house and is opened twice a day we never had any issues and it does get cold in there. Our moto is they better get used to it lol.