Right, evening all it's time once again to kick off the annual CET competition. I hope you've all had a suitably festive few days and have spent it wisely ruminating on the latest model output.
Last year Brian set hares running with this comment in the dying days of 2024:
"I'll stick my neck out and say it looks like we could have one of the most significant January cold spells in years brewing."
What transpired was a rare cooler than average month. This year there's a decent northerly in the offing which, coincidentally, gets under way properly on January 1st. It's early days but our northern contingent are already waxing their sledges.
So are we staring down the barrel of a month of the Day After Tomorrow or is there a Pint of Mild on the way following a few days of frost? To help you decide here are the ghosts of January's past:
January Average CET 4.7C 1990 – 2020
Coldest 3 since 1970
1979 -0.04
1987 0.80
1985 0.90
Warmest 3 since 1970
2007 7.00
1975 6.80
1983 6.70
Last 5
2025 3.40
2024 4.74
2023 5.20
2022 4.70
2021 3.20
Herewith follow the rules as laid out by the TWO legend 'GW':
This a reminder of how the CET competitions work for the benefit of everyone but also anyone who would like to join in for the first time. All are welcome to participate.
How do the competitions work?
Each month a new thread is opened a few days in advance of the start of a new month. Your challenge is to predict the mean Central England Temperature (CET) for the following month. The CET is the longest running temperature series and goes back to the mid 1600's. Each month I'll post some statistics about the CET for that month in recent years.
Predictions can be made either to one or two decimals (the actual data is published to two decimals). The closest person or persons to the final figure at the end of the month are declared the winner for that month. There are no prizes. This competition is just a bit of fun and the chance to amaze your fellow posters with your skill and foresight in predicting the weather (or you can just make a random guess!).
We use the Hadley data for the purposes of this competition which is maintained by the Met Office. Provisional figures are published daily with a final adjusted number usually issued on the first day of the following month.
In addition to the monthly competition there is an annual competition which runs throughout the year. The annual competition keeps a running total of the cumulative prediction errors from each month for each person. Absolute differences are used so it makes no difference if you overpredict or underpredict the CET in any given month. At the end of the year the person with the lowest cumulative prediction error after totalling each of the 12 months is declared the winner for the year. This is always a hard fought contest and requires a consistency of good predictions in order to win.
Entries after 2359 on the final day of the month will only be accepted at my discretion if I consider there is a reasonable excuse. No entries will be accepted after the 2nd of the month. There is a penalty of 0.2C for each day that a prediction is late.
Summary of important points
- Predictions can be made up to 23:59 on the final day of the month before the one to which the prediction relates. Entries may be accepted up to two dates late but with a penalty.
- All predictions should be made by email to me at [email protected]
- Once you have sent your prediction you are only permitted to change it once prior to the deadline. Any subsequent amendments will be ignored.
- You may make a prediction to either one or two decimals. You can predict the same figure as someone else.
- Where two members have the same cumulative prediction error for the year at the end of any month, the order of ranking in the competition table will be determined by which person has had the closest prediction to the actual CET in any month. If there is a still a tie I then look to the second closest prediction for each person and so on until the tie is broken. If the tie cannot be broken (very unlikely by December but can happen in the first couple of months of the year) then each person impacted is awarded the same position in the table.
Missed predictions
If a person participating in the annual CET competition does not make a prediction in any one month (including January) their prediction error for that month will be calculated as follows:
- the upper quartile (75th percentile) of the prediction errors of all the people in the annual competition who did make a prediction for that month will be calculated at the end of the month plus a penalty of 0.4C (to tie in with the penalties for late predictions);
The result of the above calculation will be used as the CET prediction error for any person who misses a prediction in a particular month subject to one further point:
- If, for any person, their average monthly prediction error for all the previous months in the year to date is higher than the 75th percentile of errors (across all entrants), then the person's average prediction error will be substituted instead of the 75th percentile figure. This override is only likely to apply to those people towards the foot of the table who have made very large errors in previous months and hence is not likely to be of significance to the overall result.
One final important point. If you want to be included in the year long competition you may not miss more than two predictions during a calendar year. If a third prediction is missed that person will be eliminated from the annual competition (otherwise it would mean 25% or more of the annual error being calculated on non-existent predictions which would reduce the credibility of the competition too much). However, that person can continue to make predictions for the purpose of the monthly competition.
That's all from me - Admin I'd be grateful if you could sticky the Thread.
Good luck everyone!
My prediction is for a distinctly chilly 3.25c
Edited by moderator
31 December 2025 12:36:19
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Reason: Not specified
Currently living at roughly 65m asl North of Cowbridge in the Vale of Glamorgan.
Formerly of, Birdlip, highest village in the Cotswolds and snow heaven in winter; Hawkinge in Kent - roof of the South downs and Isles of Scilly, paradise in the UK.