July 13th, 2026
- Mark Hunt
- 5 hours ago
- 5 min read
Hi All,
Well another bruising week in turf management with some of our Davis weather stations reporting > 67mm of Evapotranspiration (E.T) since the start of July, that's just 12 days and averages out at 5.58mm per day.
In fact, we have seen the highest frequency of 6mm+ ET days that we have ever recorded from our default Thame location in the U.K, with 6 out of the first 12 days of July exceeding 6mm+ moisture loss. Quite incredible.
E.T as we have talked about before is a calculated parameter using the Penman-Monteith equation and takes into account a number of climatic parameters including air temperature, solar radiation, wind speed and humidity.
The equation itself is shown below ;
Now, although our temperatures took a welcome dive from the high's of last week, the wind increased as it turned round to the North East and that's what has driven up the E.T to a frankly brutal level.
Yesterday, I went to Donington with my 2 brothers to watch World Superbikes. We sat in the Hollywood stand and that wind just roasted everyone. Despite copious amounts of Factor 50, we still ended up with some parts resembling lobster red and it just sucked the moisture out of us.
Brilliant to see a British winner (Tom Booth Amos a double World Supersport winner) by the way on a British bike (Triumph). Totally unreported by the Beeb and other media outlets of course, because they only mention motorcycle racing when someone gets killed at the IOM TT. Pity that.
Upon leaving we had to put on full leathers over our shorts and the like and queue to get out. Credit to Donington management, they had freshwater access points all around the track, so I adopted a trick I learnt in a past blazing hot MotoGP trip to Assen, Holland and filled my baseball cap up with water before putting it on my head. Lovely to feel that cooling evaporation. On the flipside, I have never felt so hot as we queued to leave, but hey if you throw it down the road wearing your shorts and flip flops, you won't ever want to show your legs again, that's for sure. I rejoiced in a cold shower when I got home and collapsed on the sofa and went to sleep. This heat takes it out of your body doesn't it ?
As can see from the picture, the grass at Donington has gone dormant and that's the state of many of of our turf areas whether they be domestic lawns, cricket outfields or the majority of golf course fairways that don't have irrigation. Yesterday, our local water company, Severn Trent, reported its highest ever single day of water usage.
No doubt we are in challenging times with many areas of the South East and East Anglia reporting a hose pipe ban and discretionary usage advised elsewhere. It is an emotive subject for sure, but as we have discussed before, applying drinking quality water onto turf is not likely to be a future practice if we carry on enduring heatwaves like this.
So last week I talked about the potential for a change in the weather towards the end of this week / weekend. How is that process looking now ?
Well that depends on which model you look at, but currently it isn't as nailed on an outcome as it was. For sure the cut-off low pressure will pull down cooler northerly air for a time but the models now show the emergence of a high pressure system out to the west of Ireland and that'll act to block incoming Atlantic weather fronts. That emerging high pressure will also push the previously-forecasted low pressure further east across Scandinavia as it stands now, so we will miss out on the rain associated with it. Now that is entirely-dependent on the high pressure - low pressure battle and for me it could still go either way, so let's see. But as I type here and now, it means we will see heat build again this week before the wind shifts more northward and cools us down towards the end of the week / weekend. That cut-off low will also feed in more humidity into our weather, together with an easterly-dominant wind direction and this may trigger off some localised downpours across the south of the country from Thursday onwards. 'May trigger off' being the relevant terminology.
If it pans out as currently projected, we will see heat build again from the west early next week as that high pressure nudges eastwards. This means Ireland will experience it first before it pushes across The Irish Sea into Wales and the west of the U.K and then further eastwards next week. More heat and no rain. Let us hope the forecast changes and we get some respite from these very high E.T days and continual turf stress.
I thought I'd take a look at how the cumulative soil moisture deficit pictures looks from the start of May using data from our default location at Thame, Oxfordshire.
So you can see from the graph above that the last meaningful rainfall was on the 22nd of June and since then we have had a run exceptionally high daily E.T, with only 3 days below 4mm E.T loss a day.
When we extrapolate this into a soil moisture surplus / deficit model by subtracting the moisture loss by E.T from moisture provided by rainfall, we can see how that picture looks from a cumulative perspective. This is shown below ;
So we have just crossed the 200mm soil moisture deficit threshold, that's 8" in old money and explains why un-irrigated areas are looking as they currently do and will continue to do so until we see some rainfall. Incidentally that's 3 weeks and counting since some of the wet stuff fell across this location, The Midlands and parts of The South / East of England. The west and north had more rainfall in June but in general I think July has been bone dry across the southern half of the U.K for most. For sure you'll always get the questions why you aren't trying to irrigate those areas to keep them alive ?
Well hopefully the above graphs will go some way to answer that with the volume of water required beyond the scope of availability, resource and cost for many facilities.
OK, that's me for another week, time to dig out the moving house boxes and attack another room or two whilst keeping my local wildlife in food and water !
All the best.
Mark Hunt