Why does my furnace boiler make a squealing type noise when it's getting close to cycling off during extra cold weather outside only?

We are going to need more information before we can help. What is the make & model of the boiler? Gas or oil fired? What is squealing (burner, circulator pump, etc.)?

AO Smith, Gas, sounds like squealing coming from gas valve area

Brendin, You have a strange situation. The only thing I can think of off the top of my head is the boiler either getting too hot or too much pressure. There should be a gauge on the boiler which shows temp & pressure. If you can give us those readings, it might help is diagnosing the problem.

9-10 pounds and about 160 degrees

Pressure is a bit low but nothing to get excited about as long as the gauge is accurate. Temperature is ok as well.
The only thing I can think of, since you said the sound comes from the area of the gas valve, is the valve is closing slowly. Do the flames go out like turning off a switch or do they get smaller then go out? Somewhat like turning a burner on a stove down slowly.

They go out like turning off a switch

Darn. I thought for a minute I might be onto something.

I doubt it but maybe a you tube video might help. If you can do so & post a link to the video here, I'll be glad to take a look & listen.

Does it have to be on You Tube?

No. If you prefer some other hosting site, that's fine as long as we can access it. I just mentioned you tube since that's the site many are familiar with.

911 Furnace Repair. What causes the furnace to make a squealing noise? (http://www.911furnace.com/furnace-squealing-noise.html)

Does this make sense of what you are hearing?

Being from southern CA, I seriously doubt these guys know much at all about a boiler. Unless it is in an industrial application, I doubt they've ever seen one.

No. If you prefer some other hosting site, that's fine as long as we can access it. I just mentioned you tube since that's the site many are familiar with.

Do you have an email address I can send the video to? I've attached a pic of the furnace

Bredin, check your private messages.

I honestly didn't hear any difference start to finish. Was that sound throughout the whole video some kind of motor?

Why can't we all hear the video? ;(

If you turn it up loud enough you can hear it. I only started the video when the "squealing" noise starts. It is NOT the motor. It appears to be coming from the gas valve area and only happens when the temp. outside is about 5 degrees or lower.

Has anyone checked gas pressure on both sides of the gas valve? If not, that needs to be done.

Has anyone checked gas pressure on both sides of the gas valve? If not, that needs to be done.

And how does one go about doing that?

And, if you suspect that may be the issue why would it only make the noise when it's 5 degrees or lower outside?

Low temps often result in low gas pressures. Sometimes it's simply due to temperature other times it's due to increased demand. You would need a manometer to check gas pressure.
Is this boiler natural or LP gas?

Natural, why? And how could gas pressure be corrected if low?

Regualtor could be freezing. Would need to be replaced. Gas company normally does such at no charge since it belongs to them. Call your gas company & ask them to check pressure.

Gas pressure checked an OK. Now what?

"And OK. Now what?

Was the furnace acting up when the gas pressure was checked? If not, the test means little.

No and it's not like you just have the gas company suddenly show up during the small time frame that it happens... so now what?

After 30+ years of servicing HVAC equipment I've enountered my share of intermittent problems & they are often tough to diagnose when the customer is around the corner let alone trying to do it online.

You could buy a manometer & measure the gas pressure yourself. Otherwise, I'm out of ideas. I certainly don't want to suggest just starting to change one part after another in hopes of maybe eventually finding an answer.