No surprises this month - everyone has gone hot! Though I wonder whether we all may have gone a little too low again.

Windy Willow - I couldn't spot a prediction from you; apologies if i've missed it.

Originally Posted by: scillydave 

Hadley

19.1 to the 7th

3.1c above the 61 to 90 average

2.8c above the 91 to 20 average

Originally Posted by: Gavin D 

Hi Dave,

I sent it to the email on the 29th June, but no worries my prediction is for 19.03c

Originally Posted by: Windy Willow 

Hadley

19.5 to the 8th

3.6c above the 61 to 90 average

3.2c above the 91 to 20 average

Originally Posted by: Gavin D 

Hadley

19.5 to the 8th

Originally Posted by: Gavin D 

We're back to record-breaking daily CETs again, this'll be the third such period of the extended summer.

https://www.metoffice.gov.uk/hadobs/hadcet/graphs/2026/daily_meantemp_cet_2026.png 

Originally Posted by: Retron 

A month that's rapidly becoming a class of its own.  🙂🙂🙂🙂

Originally Posted by: Hungry Tiger 

Based on a conservative reading of the 6Z GFS temperature charts I think we would be on about 21C by the 25th. I actually thought it would be higher but there are some chilly nights in there, getting into single figures.

Originally Posted by: Rob K 

Anything over 19C is incredible if you ask me.  🙂🙂🙂🙂

Originally Posted by: Hungry Tiger 

If we end on 20, after such a cracking June, we'll only need a 15.8 August to beat last year's hottest CET summer.

Originally Posted by: Bertwhistle 

Well we're into 20s territory after today- judging by current progress perhaps 20.3 (Stonyhurst has joined the heat party today but as expected, Rothamsted is down a few notches)

Originally Posted by: Bertwhistle 

Today's maxima:

Stonyhurst: 31.7

Pershore: 34.2

Rothamsted: 31.3

So a very toasty CET max. Are the minimum values taken from this morning or tomorrow morning? I thought it would be tomorrow as the overnight minimum is usually credited to the previous day but the Hadley page says "there is always one more minimum than maximum" which suggests the reverse!

Originally Posted by: Rob K 

I've never really understood that statement Rob. If taken literally, in a 365 day year, there would be 365 maximum temperatures and each month would have one more minimum, meaning the year would have 377 minima, which is obviously nonsense.

I always understood that the minimum was accredited to the 24 hour period preceding a measurement for a given day, so e.g. on 2nd of the month, the period 9GMT on 1st to 9GMT on 2nd would provide the minimum for the 2nd.

The maximum is more obvious but could potentially occur the day after, before the reading.

Originally Posted by: Bertwhistle 

Not sure what you mean by your bolded line, as that would not be the previous day (if it was the previous day then the 0900 reading on the 2nd would count for the 1st).

Anyway I have found a (hopefully) definitive answer on the Hadley page: https://www.metoffice.gov.uk/research/climate/maps-and-data/data/haduk-grid/datasets

Maximum: Maximum air temperature measured between 0900 UTC on day D and 0900 UTC on day D+1 (ºC)

Minimum: Minimum air temperature measured between 0900 UTC on day D-1 and 0900 UTC on day D (ºC).

So that would mean that the max reading at 0900 on the 2nd would be credited to the 1st, and the min reading would be credited to the 1st. Which makes sense as usually the maximum would have been on the 1st and the minimum in the early hours of the 2nd.

Obviously it can sometimes mean that if there is a sudden overnight warmup, the max is credited to the "wrong" day, or if it is still very cold just after 9am on one day and it then warms up, the cold minimum gets double counted.

Anyway this does explain the line about there being "always one more minimum than maximum", because the minimum for today (11th) was already known from 0900Z today, but the maximum for today will not be officially known until 0900Z tomorrow. It's talking about the rolling average, because on any given day N it will always have N minima but only N-1 maxima (because the maximum for day N is only known on day N+1). Simple! ;)

Originally Posted by: Rob K 

Not sure what you mean by your bolded line, as that would not be the previous day (if it was the previous day then the 0900 reading on the 2nd would count for the 1st).

Anyway I have found a (hopefully) definitive answer on the Hadley page: https://www.metoffice.gov.uk/research/climate/maps-and-data/data/haduk-grid/datasets

Maximum: Maximum air temperature measured between 0900 UTC on day D and 0900 UTC on day D+1 (ºC)

Minimum: Minimum air temperature measured between 0900 UTC on day D-1 and 0900 UTC on day D (ºC).

So that would mean that the max reading at 0900 on the 2nd would be credited to the 1st, and the min reading would be credited to the 1st. Which makes sense as usually the maximum would have been on the 1st and the minimum in the early hours of the 2nd.

Obviously it can sometimes mean that if there is a sudden overnight warmup, the max is credited to the "wrong" day, or if it is still very cold just after 9am on one day and it then warms up, the cold minimum gets double counted.

Anyway this does explain the line about there being "always one more minimum than maximum", because the minimum for today (11th) was already known from 0900Z today, but the maximum for today will not be officially known until 0900Z tomorrow. It's talking about the rolling average, because on any given day N it will always have N minima but only N-1 maxima (because the maximum for day N is only known on day N+1). Simple! ;)

Originally Posted by: Rob K 

That's very helpful (and something I have often had trouble with)

Just for complete accuracy shouldn't the bit I marked read "2nd" not "1st" or have I still not "got it" ?

Originally Posted by: lanky 

If you measure the max and min for the past 24 hours at 0900Z on the 2nd, the minimum you record is the minimum for the 2nd, and the maximum is the maximum for the 1st.

Originally Posted by: Rob K