September 1st dawned with the sun burning through thick mist after a chilly night – a perfect start to the autumnal season, after what will be remembered as the hottest and driest summer we’ve ever experienced here. The Met Office quickly ran the numbers and declared it as the hottest, sunniest and one of the driest across Wales since their records began. There are some easy-to-grasp colour-coded maps, which highlight this.
Here’s an interesting comparison between the summer of 1976 and 2026
Of even more interest to me was discovering the maps on the UK hydrological survey site, indicating the groundwater deficit – it turns out we will need a lot of rain over and above our typical autumnal and winter deluges to bring these stores up to their typical wet level.
Which got me thinking – just how much, and when did it begin to become a problem here? To try to answer this, I’ve compiled our own mean monthly rainfall data from the last 13 years and shown the actual monthly rainfall over the last 12 months. With any monthly surplus or deficit over the mean figure to highlight this:
09/2025: 243 mm mean:166 mm monthly surplus: 77mm
10/2025: 226mm mean: 207 mm monthly surplus: 19mm
11/2025: 379mm mean: 226 mm monthly surplus: 153mm
12/2025: 341mm mean: 268 mm monthly surplus: 73mm
01/2026: 262 mm mean: 212 mm monthly surplus: 50mm
02/2026: 227 mm mean: 207 mm monthly surplus: 20mm
03/2026: 150 mm mean: 152.7 mm monthly deficit: 2.7mm
04/2026: 95.5 mm mean: 96.1 mm monthly deficit: 0.6 mm
05/2026: 91.8 mm mean: 97 mm monthly deficit: 5.2 mm
06/2026: 134 mm mean: 101 mm monthly surplus: 33 mm
07/2026: 8 mm mean: 95 mm monthly deficit: 87 mm
08/2026: 74mm mean: 142.5mm monthly deficit: 68.5 mm
Thus, from last September, months in surplus equated to a surplus of 425mm. Months in deficit, just 164mm. Overall surplus for the year of 261 mm
However, the fact that the deficit months coincided with this summer’s heat and sunshine, meant that much water was lost from the higher levels of the ground via increased evapotranspiration. And in any event (in a lightbulb moment for me!) our groundwater will always try to run downhill – though this can be an incredibly slow process, taking many years or decades, particularly in the type of shale rock that underpins our land.
These rocks are (I now know!) Silurian-age turbiditic mudstones, shales, and siltstones, primarily belonging to the Cwmere Formation and the Rhyddlan Formation. They were deposited roughly 430 to 440 million years ago as deep-water sediment flows within the ancient Welsh Basin. Because the region underwent intense folding and low-grade metamorphism during the Caledonian orogeny, the shales are hard but highly fractured and brittle. This brittle nature is responsible for the rapidly draining, stony shale soils characteristic of our local hillsides.
As the month progressed, some rain fell every day, but it wasn’t until September 12/13th that we had our first significant rainfall in months – 25 mm, which will have begun the restoration of groundwater.
But perhaps too late for many of our moles and grassland fungi: their populations, I fear, will have collapsed.
Tunnels have collapsed into deep fissures in most fields, and the only significant number of molehills at the moment is close to the stream, where one industrious mole has dug into streamside rubble deposited by recent years’ spates, after storm Callum cut the bank back years ago.
At last we could put away the eaves-collecting rain containers, and take down the temporary gutters we’d fixed to the barn.
Plants began to revive, and on a rare sunny day, I completed our annual honey harvest, which I’ve turned into this short video to remind myself, and anyone interested, of the system I now use.
There were still large groups of swallows flying around the house and big sycamore, particularly in 20-minute bursts, around 8.00 am and later around 5.00 pm. Woodpeckers and buzzards were also evident.
Cyclamen hederifolium began to flower, with as many blooms as ever, and despite the rain we still enjoyed some special moments of cloud and light towards dawn and dusk.
Highlighted maximum and minimum records for previous Septembers are listed below, which illustrate it’s only rarely a very dry month, and levels of light as recorded by the PV output can vary quite a lot:
2014: 13.7 mm, 24 dry days (!) NA
2015: 105.8 mm, 13 dry days, PV – 354.6 KWH
2016: 173.5 mm, 10 dry days, PV – 272.9 KWH
2017: 237.5 mm, 6 dry days, PV – 264.7 KWH
2018: 172.1 mm, 9 dry days, PV – 307 KWH
2019: 202.2 mm, 9 dry days, PV – 333 KWH
2020: 116.6 mm, 16 dry days, PV – 351.9 KWH
2021: 143.8 mm, 14 dry days, PV – 293 KWH
2022: 205.6 mm, 13 dry days, PV – 294 KWH
2023: 223.9 mm, 7 dry days, PV – 294.9 KWH
2024: 156 mm, 7 dry days, PV – 254 KWH
2025: 243.1 mm, 10 dry days, 307.6 KWH
2026: