Record Cold Likely

[Bill O]

It was -22F at my place in Vermont in the Champlain Valley. I think Burlington and St. Johnsbury were both colder than -15F. Both set daily records.

Edit: I just saw the forecast for Thursday night. Impressive. Forecast for Saranac Lake is -35F and the discussions are talking about records. Looks like this is going to be a valley event with ideal radiational cooling.

[treant985]

It was -22F at my place in Vermont in the Champlain Valley. I think Burlington and St. Johnsbury were both colder than -15F. Both set daily records.

Edit: I just saw the forecast for Thursday night. Impressive. Forecast for Saranac Lake is -35F and the discussions are talking about records. Looks like this is going to be a valley event with ideal radiational cooling.

There aren't too many reporting stations in VT....I pulled the following lows from Tues and Wed morning from the NY state page, which lists most of the VT stations that report daily:

BURLINGTON VT -11
MORRISVILLE VT -13
MONTPELIER VT -10
ST JOHNSBURY VT -11
SPRINGFIELD VT -14
RUTLAND VT -15
BENNINGTON VT -8

However, I found another NOAA page with the following:

THE LOW TEMPERATURE AT BURLINGTON VERMONT REACHED -18 DEGREES AT
7:15 AM TODAY. THIS SETS A NEW RECORD LOW TEMPERATURE FOR THE DATE...
BREAKING THE OLD RECORD OF -14 DEGREES SET IN 1989.

THE LOW TEMPERATURE AT SAINT JOHNSBURY VERMONT REACHED -24 DEGREES
TODAY. THIS SETS A NEW RECORD LOW TEMPERATURE FOR THE
DATE...BREAKING THE OLD RECORD OF -16 DEGREES SET IN 1989.

THE LOW TEMPERATURE AT MONTPELIER VERMONT REACHED -17 DEGREES
TODAY. THIS TIED THE PREVIOUS RECORD LOW TEMPERATURE SET IN 1989

...so obviously the NY state reports were off. The hourly reports at the NOAA seem to confirm the colder readings, except they list -22 for St. Johnsbury.

May I ask where you saw discussion about possible records falling on Friday morning? I did a google news search hoping to find mention of this morning's -35 reading at Saranac Lake, but I came up empty.

edit: Mt. Mansfield in VT recorded -28 yesterday morning according to an NOAA release I just read.

[Bill O]

It was in the Burlington NWS discussion issued at 355pm. Here

SOMEWHAT OF A DEJA VU WEATHER SCENARIO WITH SECONDARY SURGE OF COLD
AIR EXPECTED TO MOVE INTO THE AREA ON THURSDAY AND PERSIST THROUGH
FRIDAY. FIRST LOOKING AT INCREASING CLOUDS LATER TONIGHT AS
SHORTWAVE TROUGH DROPS SOUTHWARD INTO THE AREA. THERE COULD EVEN BE
SOME SNOW SHOWERS OVER THE AREA AFTER MIDNIGHT AND THROUGH THE FIRST
PART OF THURSDAY. WINDS WILL BE INCREASING FROM THE NORTHWEST AND
GUST AS HIGH AS 30 MPH. AT THE SAME TIME...STRONG COLD AIR ADVECTION
WILL NOT ALLOW TEMPERATURES TO CLIMB TOO MUCH ABOVE THE MINIMUM
VALUES TONIGHT. THUS LOOKING FOR HIGH TEMPERATURES GENERALLY IN THE
SINGLE DIGITS ABOVE ZERO WITH SOME AREAS NOT EVEN MAKING IT TO ZERO.
THUS THE COMBINATION OF UNSEASONABLY COLD TEMPERATURES AND GUSTY
WINDS WILL CREATE WIND CHILL VALUES REACHING ADVISORY CRITERIA AND
ONCE AGAIN IT WILL BE A SITUATION WHERE THE EVENT WILL OCCUR DURING
THE DAY. CLEARING SKIES AND DECREASING WINDS THURSDAY NIGHT WILL
SET THE STAGE FOR ANOTHER STRONG RADIATIONAL COOLING NIGHT. THUS
LOOK FOR TEMPERATURES TO PLUMMET TO RECORD LEVELS WITH SOME AREAS
SEEING READINGS AS LOW AS 30 TO 40 BELOW. THE RECORD LOW
TEMPERATURES EXPECTED WILL COME ON THE HEELS OF SOME RECORD LOW
MAXIMUM TEMPERATURES ON THURSDAY...MUCH LIKE WHAT WE SAW ON TUESDAY
INTO WEDNESDAY MORNING. COLDEST CORE OF AIR AT 850 MB MOVES QUICKLY
EAST ON FRIDAY AND WITH FULL SUN AND LIGHT WINDS...WE SHOULD BE ABLE
TO GET HIGH TEMPERATURES UP INTO THE TEENS. THIS WILL THEN START A
WARMING TREND GOING INTO THE WEEKEND AND PERSISTING THROUGH THE
FIRST HALF OF NEXT WEEK.

Edit: Burlington NWS also mentions -40F in a new Special Weather Statement

[KD Talbot]

I have some questions about these cold temps. Can temps this cold be accurately measured with a mercury thermometer? I thought I had read that mercury becomes innacurate at these low temps. I was in Rangeley a couple of years ago and the morning temp read -40 on a mercury thermometer. Could this be?

Part two- If they're not accurate, how do we know that the reports coming in are accurate? Couldn't they be coming in from a weather novice like myself? Or do they have to be verified?
KDT

Edit: I guess anything reported by the NOAA is from a reliable source, but I'm saying what you might hear on the local news/weather reports.

[Bill O]

I have some questions about these cold temps. Can temps this cold be accurately measured with a mercury thermometer? I thought I had read that mercury becomes innacurate at these low temps. I was in Rangeley a couple of years ago and the morning temp read -40 on a mercury thermometer. Could this be?

Part two- If they're not accurate, how do we know that the reports coming in are accurate? Couldn't they be coming in from a weather novice like myself? Or do they have to be verified?
KDT

Edit: I guess anything reported by the NOAA is from a reliable source, but I'm saying what you might hear on the local news/weather reports.

Most of the data mentioned above comes from airport automated ASOS stations. They use thermistors that are certified for NWS use. No mercury or alcohol involved, just electricty passing through a resistor.

The local media is pretty lazy, they get most of their data from NWS sites, or from sites like Weather Undeground. I wouldn't worry too much about mercury, almost nobody uses it...you can barely buy the stuff anymore. Co-op observers are issued alcohol filled minimum thermometers. Newer co-op observers are using high end Davis weather stations.

I'm not sure I answered your question. Official data comes from NWS offices, airport ASOS, Mount Washington, and co-op observers. And maybe some call in reports from weather enthusiasts, but any records will be verified by the NWS.

[KD Talbot]

Thanks, Bill. Yes, that answers part 2, but, was I getting an accurate reading from a mercury thermometer when I was in Rangeley? It seems very difficult for temps to reach -40 at this latitude, even on MW.
KDT

[Bill O]

Thanks, Bill. Yes, that answers part 2, but, was I getting an accurate reading from a mercury thermometer when I was in Rangeley? It seems very difficult for temps to reach -40 at this latitude, even on MW.
KDT

I'm not sure. I read that mercury freezes at just above -40F. Could it have been a nice alcohol thermometer? I'm guessing it was because nobody would make a mercury thermometer that goes that cold if they know its just going to turn to solid metal.

If a thermometer existed that used liquid water you wouldn't make the scale below 32F.

[KD Talbot]

I'll have to check into that now. I was pretty sure it was mercury, but I guess it could have been alcohol, if they look the same. If it were alcohol, it would provide an accurate reading?
KDT

[Bill O]

I'll have to check into that now. I was pretty sure it was mercury, but I guess it could have been alcohol, if they look the same. If it were alcohol, it would provide an accurate reading?
KDT

If it was alcohol it should be accurate. I'm not guaranteeing anything. Just take a look at the bulb on the end. Mercury will look silver/metal, alcohol will be red.

NWS thermometers only have to accurate to within one degree celsius, that's 1.8F.

[treant985]

Based on what I've read, it could have been a mercury thermometer, but if it was reading -40, then it probably wasn't "NWS accurate." Almost all substances don't contract evenly right at their freezing point; I think mercury's freezing point is like -38F, but it probably wouldn't be accurate after -35F or so. It may have been somewhere colder than -35F, but with a combo of a slightly inaccurate thermometer with the mercury behaving weird right at the freezing point could've made it show -40F.

Are the red ones always alcohol? I was never sure if it was possible to dye mercury somehow. Just to throw it out there, I've also seen blue and yellow alcohol ones, so they can be pretty much any color.