Hello,
the cold tightens the wood fibers and as a result the reed requires significantly less air. That can really be very annoying. What I make in such situations is to take out the reeds one by one, apply very small quantity of tallow and rub gently the reed so that it heatens from the body temperature. Usually the problem is with reed of the chanter, but sometimes such a procedure may be necessary for the reed of the drone, too. After this you place the reeds and begin to play without dalay so that you can keep the heat through your air. Some bagpipers have special reeds for cold weather which require more air than usual and when it's cold they behave in the right way.
By flattering, you mean it is too low??? The hole in question is not used in Bela sum, Bela. It is the seventh hole from top to bottom, right???
I am quite, quite sure this problem is due to the temperature change.
1) See if the problem persists in normal conditions;
2) See if there is any tallow, wax or other substances in the whole;
I suppose that if you play in normal temperature the tone will come to the right pitch.
If that doesn't help I would recommend you to try some standart procedures: rotate the reed by difffernt degrees and see if this makea a better sound , see if you have pushed the reed well into the chanter, see if there are too may or too less threads bound round the reed, see if you have not tuned the bagpipe too low or too high. Sometime just small change of the bagpipe tune slightly above or under E helps greatly.
Is the bagpipe new? Has it shown such problem before or it begins with the playing in the cold?
Greetings,
Kostadin