September 17th, 2025

Hi All,

Well, a late blog this week and a short one. A consequence of my twice annual visit to see the 'Blonde Assassin' in Nottingham hospital for my shoulder work (she's a genius) combined with being in catch-up work mode after lots of time spent away on hols. As I type this it's as grey as grey can be can be outside with another slug of rain due soon. September is already the wettest month of 2025 for us here in Market Harborough and we are only on the 17th of the month. Nothing like the rainfall of September 2024 mind when a cut-off low brought us 166mm over 3 days, but on some of my local weather stations we are already over 100mm for the month to date. (most are around 75mm)

Video from lightningmap.org

The reason for the variability in rainfall was the occurrence of recent thunderstorms as shown by the excellent lightningmap.org graphic above. We got clattered.

One of the other reasons for the delay in putting this blog together was yet again, significant variability in the GFS forecasts with every update showing a changing weather picture, however, the last 4 updates have been reasonably stable. No point in publishing a weather blog if it is woefully inaccurate.

Walking through Fineshades Wood, Corby yesterday afternoon as part of an elevated exercise regime, necessary because of my Bara Brith intake over recent weeks :). It definitely feels like early autumn out there but you know despite the heavy rainfall of late, everywhere was still really dry and one reason for that is the wind.

Prodata Reports - Climatic Summary - September 2025 - The Oxfordshire, Thame

Since the weather changed at the end of August, we have had significant wind strength primarily from the south west. That wind, combined with mild temperatures typical of September has been driving significant daily E.T levels, so areas are drying out quickly in-between the rainfall events. The graphic above from our Prodata Reports software shows both the significant daily ET levels and the dominant wind direction.

Nature's summer migrants are heading home now, with all of the Rutland Osprey's departing recently for their long migration back to Gambia. Swallows and Martins are still hanging on, feeding up their last brood before waiting I think for a change in wind direction before heading south (they'll get that shortly me thinks). I have still heard the occasional Chiffchaff over at Rutland Water, but soon that song will be absent. Personally I love the autumn, the changes in the landscape, the colours and the smell, as well as the appearance of Mushrooms and other Fungi. Last year I failed to find Flyagaric's locally, this year I'll try again. They fascinate me.

Animated GIF courtesy of tropicaltidbits.com

Onto the weather.....

So currently since the end of August to be precise, the jet stream has kicked up a few gears and rattled Atlantic low pressure after low pressure across the U.K & Ireland and onto Scandinavia. Now don't get me wrong, the arrival of significant rainfall is a start on the long road to recovery from drought status (we have a long way to go) but some nice, settled autumnal weather would be nice as well.

Well that looks like it could be on the way after we get this week and a potentially wet start to the weekend over with. So this week we continue the sunshine and showers theme accompanied by a brisk south westerly wind. As we move into the weekend, high pressure starts to build in The Atlantic. This does two things, one it settles things down a tad, but it also changes the wind direction round to the north from Sunday, dropping the day and night time temperatures significantly. So whereas we are more like high teens this week, we will drop to low teens by Sunday, it'll feel noticeable chillier.

As it stands now, that high pressure looks to build next week and bring some drier and settled conditions across the U.K, Ireland and across The North Sea in Denmark. It won't at this stage be a warm, high pressure, more like 15-16°C during the day and down to single figure temperatures at night. Looking further down the line, there's a suggestion that warm air may fill this high later next week and take us into October with some very warm and settled weather. Subject to change of course but one to watch.

Agronomic Notes

Now earlier in the summer I compared summer 2025 so far (at that stage) with 2018 and remarked that in my view 2025 was worse from a drought perspective because it started so much earlier than 2018.

Whilst this is definitely true, i.e. we have a much worse water or lack of water situation this year vs. back then as I type, it is only one aspect. I was having a chat/debate via LinkedIn with Richard Allen (of Ecobunker fame) and he sent me 2 images of a local golf course, one from 2018 and one from 2025. The difference in appearance is striking and highlights the elevated drought stress in 2018 vs. 2025.

Hmmm I thought, let's look into this....

So, I pulled up some historical information from our default location at The Oxfordshire and specifically I looked at 3 parameters, rainfall, E.T and mean temperature.

Now, it isn't a coincidence in my mind that 3 of the hottest, driest summers have occurred since 2018. We are on an upward trend currently and frankly speaking, I don't give a toss about the arguments wherefore and why, it is irrelevant to this particular discussion. The pure facts are, we are seeing hotter and drier summers since the turn of the century, the frequency is increasing and that is what we have to deal with as turf managers. By the way, whilst I am in semi-rant mode, if you are a conspiracy theorist lover, do me a favour and unsubscribe from this blog, I just can't be doing with you.

E.T, Rainfall and average soil moisture surplus / deficit comparison - Thame, U.K

Back to the facts and data.

I first up I pulled together the E.T and rainfall stats and then calculated the soil moisture surplus (SMS) / deficit (SMD) in mm. Now this is just for the summer period, defined meteorologically as June, July and August and the summary table is shown above.

What we can see is from an E.T perspective, for this location, summer 2018 and summer 2025 were very similar in terms of calculated total moisture loss by E.T, 335mm vs. 329mm respectively. Summer 2025 had the highest June E.T loss figure, Summer 2018 the highest July figure and they were pretty similar for August (Summer 2022 the highest)

Next the rainfall stats and here you can see I think the reason why those images above are as they are.

Summer 2018 (for this location) was significantly drier than summer 2025, 60.8mm vs. 124mm respectively. That means that the calculated soil moisture deficit was also higher for 2018 than 2025, -275mm vs. -205mm. During Summer 2025 it is also worth pointing out that the rainfall described in the table above came just at the right time to keep things from 'going over', in summer 2018, that didn't happen.

I did say at the start of this fact-chomping exercise I would also look at the average air temperature for the respective summer periods for this location. From this perspective, we can see that Summer 2025 was the hottest yet of the current period by some margin for this location.

So what can we conclude ?

Well in my mind, what we can see is that from a pure turf management perspective, summer turf management is about managing the balance between E.T and rainfall.

I know no surprises there but the point I am making is that it is this balance that is critical to manage rather than outright temperature. You would think the two are interconnected but it isn't a given. In the recent past when we have had record high temperatures, we haven't had record high E.T's on the same day. The reason being that E.T is dependent on a whole host of other factors aside from just temperature, the most significant of which are wind speed and humidity. So a calm, humid, hot 40°C day will have a lower E.T than a windy, dry air, 33°C sort of day. The latter presents much more issues for the turf manager than the former.

No surprises there you might say, but then I'll ask you this...

How many of you manage your turf's irrigation by measuring your actual E.T at your location ?

And if the answer is you don't, then I would be concerned because that's where we need to be surely ?

Coming down the line we are going to be held accountable for the water we use in the future and to maximise efficiency, we need to be really. You might argue that measuring soil moisture is how you manage irrigation and maximise irrigation efficiency (and it is a great aid for sure), but I would put forward the counter-argument, that unless you know how fast your soil moisture status is changing, you only have half of your soil moisture picture.

It is an interesting debate to be had, of course, the above is just my opinion and you know what they say about opinions :). It is hopefully designed to get you and your club's management thinking about the future. I know many of you are and have already taken strategic steps for future-proofing your facility. That's great and I applaud you, but there is I think more work to be done in our industry.

Off I hop from my well-trodden soapbox, All the best.

Mark Hunt