Hadley

18.9 to the 14th

2.9c above the 61 to 90 average

2.6c above the 91 to 20 average

Hadley

18.7 to the 15th

2.7c above the 61 to 90 average

2.4c above the 91 to 20 average

So still at 18.7°C which is thanks to the one day cooler interlude still delivering a daily mean only two tenths shy of the average. In fact the coolest day has only been .3 below through the first half. Today is a lot warmer again and we have perhaps two potentially hot days but a potentially longer run of warm nights. If we average 20.2 for the 4 days including today that'll add enough to tip the CET just over 19- but only based on an exact 18.7. If it's slightly less, we'll need slightly more. 

It would be nice to tip past the 19, even though it'll be sure to drop during the last third. But it would need to average no more than about 16.3 daily for the overall 18+ to be lost. We may lose the warm days, but if we can average 14 per night at the three stations, high 18s by day will be enough.

Hadley

18.7 to the 16th

2.7c above the 61 to 90 average

2.3c above the 91 to 20 average

Stonyhurst may not even max out at 20 today so it may be that the 19 is off unless the very warm night here locally was picked up at the two S stations and we get some high twenties tomorrow. I'm confident the CET will rise after tomorrow, but not by as much as I'd hoped. Each degree above yesterday's 18.7 (the day itself was only 18.4) will only add about 0.06 on I think (as we're close to 20 days) so to get to 19 it now looks as if we'd need 5 degree days above 18.7 and if today scrapes a 20 we'd still need about 22.4 on Friday- not impossible, but unlikely. Somewhere shy of 18.9 I suspect overall up to 19th.

After that, a run in the 15s and 16s before maybe picking up a bit in a week's time.

Hadley

18.8 to the 17th

2.8c above the 61 to 90 average

2.4c above the 91 to 20 average

Surely another heat burst in the final third would make a 19 degree month likely? There have only ever been four 19 degree months in history (July 1983, August 1995, July 2006 and July 2018), so it would be an achievement, especially for it to happen so easily.

We'll see but I don't think it's likely to happen based on current model output. I think it's more a question of whether it holds above 18c.

HadCET 18.9°C to 18th.

Hadley

18.9 to the 19th

2.9c above the 61 to 90 average

2.4c above the 91 to 20 average

Held well yesterday- was 19.1°C still. So with 19 days averaging 18.9°C I have calculated that an average for the remainder of the month of 16.58 would be enough for an 18 overall, giving us a good position going into August of a hot summer overall (we'd only require an August mean of 16 for this).

Each day now above that 16.58 will strengthen that position, and obviously each day below would decrease the likelihood of an overall 18. It was a warm night here again last night(>17) but I have no idea what the stations were like. Today has only reached 20 so far even with afternoon sunshine so I suspect today could be lower although MetO forecasts for the 3 stations suggest an average a little below 18 between them across the next 7 days. Even a 17 would be more than enough. Let's see.

Hadley

18.9 to the 20th

2.9c above the 61 to 90 average

2.4c above the 91 to 20 average

Warm nights providing belt and braces. The CET max yesterday didn't reach 21°C. Only 16.4 needed for an 18 overall.

Hadley

18.8 to the 21st

2.8c above the 61 to 90 average

2.3c above the 91 to 20 average

Not bad and 9 days left. 🙂🙂🙂🙂

Hadley

18.7 to the 22nd

2.7c above the 61 to 90 average

2.1c above the 91 to 20 average

In fact, the MetO forecast estimates for Rothamsted, Stonyhurst and Pershore suggest an overall average for the next 7 days (including today) of about 18.3. That's 14 full degree days above the minimum required, suggesting a likely 18.5 by the end of the period, largely boosted by 20+ degree values at the two southern stations.

There will then be a final 2 days to adjust. Even if these two days are in the 15s we would be looking close to 18.3. 

In that scenario, this is what we would need in August to beat recent hottest summers, (checked if adjustments were required slightly to allow for only 30 days in June- it made little difference); each would require an above average August, but not a scorcher, except 1983.

1983: 16.0

2003: 16.6

1995,2006 and 2022: 16.7

2018: 17.0

August 1997 is now added to that list (the old CET tables had it below 19).

Yes, I forgot about that one since they changed the CET (I still don't know why they did that, to be honest).

There have been a few changes in that round of 'updates' Scott. June 1976 is the one that stands out for me as it was the first modern 17 degree June but it got adjusted down. August 2013 went in reverse from 16.9 to 17.0 so clearly there isn't a one-way adjustment protocol going on.

I thought there was an explanation at some point but can't remember what it was. 

Anything over a CET of 18.0C imo is a very good- warm to hot summer months.   🙂🙂🙂🙂

Hadley

18.6 to the 23rd

2.6c above the 61 to 90 average

2.0c above the 91 to 20 average

We do indeed appear to be headed for a low 18s °C finish. Even if we get unlucky/lucky (depending on local drought situation) and one of the cloudier, wetter scenarios plays out next Tuesday and/or Thursday, higher overnight temperatures will probably mitigate the impact on the CET.

That August need not be particularly hot for summer 2025 to challenge the hottest on record is testament to the variability of the British summer. Even 1976 had some markedly cooler episodes between the heatwaves. If only those had delivered more in the way of rainfall!

So, what of the prospects for August 2025? To be honest I'm seeing contradictory signals. There's not much pointing toward long runs of high pressure and hot weather, but neither is there a clear signal for predominantly unsettled and/or cool weather patterns. Perhaps, then, the abundance of over 1°C above normal sea surface temperatures around not just the UK but most of Europe might be what allows summer 2025 to contend with the likes of 2018?

Hadley

18.6 to the 24th

2.6c above the 61 to 90 average

2.0c above the 91 to 20 average