Fickle things sea trout. A perfect night on the Monday – overcast and warm with a low clear river, and, although there weren't that many fish evident, we saw enough jump to keep us interested throughout the night, and we ended up with four fish between us to 4lb, plus a few others that came detached. Prospects looked good for Tuesday night, although the forecast did hint of rain. I started late, but first run down the rocky pool and I rose a sea trout at the head of the rock, and landed a hefty grayling on a small Muddler just as the first drizzle arrived. The portents were good. Before I'd unhooked it, I decided the rain that had just arrived was now heavy enough to retreat to the car and switch my fleece for my wading jacket. Good call. Did I say hint of rain? For the next five-and-a-half hours rain pelted out of the black night. By two o'clock in the morning, the peak of my cap had become so wet that my head torch became damp under my hood and shorted out, so I had to return to the car to change flies or set up (must remember the back-up torch, next time!). Not that I minded: I could sit down on the tail-gate and shelter under the hatchback as the rain beat down on it like a tin drum in a calypso band. I admit to being deflated, though, when Banjo, my trusty spaniel, whined that she wanted to climb up and shelter and sleep off the rain in the back, but I didn't blame her – you wouldn't put a dog out on a night like this. So what was I doing still fishing? Well, my last night on this beat last year was exactly the same: incessant rain. However, I did catch a six-pounder at 3 o'clock in the morning on a surface lure. It was that thought that kept me going. At least it was still warm.

So, keeping a close eye on the river level and its colour, I continued manfully, and damply. I tried small flies under the surface, big flies deep, small flies deep, I tried surface lures, sunk lines, and I tried snakes and Waddingtons. I tried different pools, I tried favourite hot-spots, reliable lies. In all this time I didn't feel, see or hear a single fish.

Had they all moved on, aware that the river level was set to rise? Or had the rain put them down? I think I got my answer when I switched on the car's ignition and the radio announced the shipping forecast as I rolled down the lane, water gushing like geysers from my tyres as I sloshed through the sodden meadow. "Irish Sea: Low, 911, moving east". The forecast on the television last night hadn't mentioned the intense low pressure moving in; the TV maps rarely feature the isobars and pressure systems these days. Fish don't mind rain, but in my experience they don't like a rapid drop in air pressure, and this had been a particularly deep fall from the settled conditions the previous night, possibly around 100 millibars. Sea trout are fickle enough normally, never mind on the back of a rapid air-pressure drop.

I've seen it many times with wild fish. Humans are so ignorant of air pressure, yet fish are so sensitive. Often the fishing goes off - they refuse to bite, or if they do, they are half-hearted about it. No-one can understand why, until the next day, when in rolls the cloud with the cold front. The fish were well aware it was coming, having experienced the (uncomfortable?) drop in pressure that precedes it.

So, a lesson learned from the modern TV forecasts: apart from rain, we fishermen need a little more background detail; in future, I'll be keeping an eye on the pressure systems that bring that rain, too. However, the million-dollar question is: had I known that a deep low was approaching fast, would I have stopped fishing? Whatever we believe to be the effect of air-pressure on sea trout, we do know that we can't catch them in bed.