Winter 1828-29 was a peculiar winter with a very mild December, a notably cold January and a fairly average
February.
December 1828: 7.4 (+4.2)
January 1829: 0.3 (-2.2)
February 1829: 4.3 (+0.2)

December 1828 is the 7th mildest December ever recorded. The period 4th-24th December was exceptionally mild: 9.0C
January 1829 is joint 27th coldest ever recorded. The period 16th-25th January average: -2.9
The drop in CET between December and January is the largest ever recorded
December 1828 was wet whilst January and February were pretty dry.
The modern day equivalent of this winter would be 1986-87.

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"The weather during the last two or three days has been mild to an extraordinary degree in this neighbourhood. On Monday, the thermometer stood, at one period, as high as 56F, this may be considered as remarkable, when, as has been stated to us be the case, it is on record that during the "dog days", last summer, it stood as low as 45F.
Flies are still commonly observed in most houses and yesterday we actually saw a wasp that had crept forth from its winter retreat and was essaying to poise itslef on its "gauzy pinions"

Public Ledger 26th December

"The weather here still continues unprecedently fine for the season. We have not yet experienced any of the usual concominants of winter; the Cambrian hills have exhibited some hail this week and the winds have been and still continue bisterous but in other respects it is spring; the fields retain their verdure and cattle lack no fod in the pastures. This is an important, as from the immense destruction by the floods of last summer in the hay and other crops, great apprehension was entertained of a scarcity in the article of fodder, which, providentally, is much lower than usual at this time of year.

Chester Chronicle 17th December

"After an autumn almost unprecedened for a long season of fine clear and dry weather, we have for several weeks past had a continuance of cloudy and wet weather, with high winds, but little or no frost. The absence of the latter has produced a kind of second spring with some kind of plants, amongst others, the furze upon the fells is in several places covered with yellow bloom."

Newcastle Chronicle 25th December

"The farmers are present mild weather, as the insects and particularly the slugs, are getting numerous and strong. The slugs are attacking and injuring the young shoots of wheat. Frost is anxiously looked for to destroy these active enemies of plants in their young state."

Public Ledger 2nd January
Temperatures at Stratford. east London

December January
1. 41f, 28f 48f, 35f
2. 42f, 32f 43f, 32f
3. 50f, 46f 42f, 34f
4. 54f, 49f 35f, 32f
5. 54f, 34f 37f, 27f
6. 57f, 40f 36f, 30f
7. 45f, 39f 40f, 32f
8. 47f, 34f 34f, 32f
9. 44f, 37f 38f, 33f
10. 50f, 49f 41f, 30f
11. 50f, 47f 38f, 32f
12. 53f, 48f 38f, 31f
13. 54f, 47f 38f, 33f
14. 50f, 38f 40f, 37f
15. 49f, 40f 40f, 34f
16. 52f, 50f 34f, 30f
17. 56f, 50f 35f, 28f
18. 65f? 41f 36f, 18f
19. 51f, 46f 32f, 20f
20. 52f, 49f 31f, 24f
21. 51f, 40f 31f, 22f
22. 55f, 48f 31f, 24f
23. 52f, 43f 24f, 18f
24. 52f, 42f 23f, 18f
25. 45f, 27f 33f, 20f
26. 43f, 31f 45f, 38f
27. 48f, 36f 42f, 33f
28. 45f, 37f 41f, 30f
29. 39f, 33f 40f, 31f
30. 45f, 39f 40f, 35f
31. 48f, 37f 38f, 28f