1. Go early, or stay late
Water temperatures are lowest in the morning and cool off in the evening, so fish will be feeding most at these times of the day. If you can, plan your trip either first thing in the morning or last thing in the evening and you'll increase your chances of catching. The toughest time will be lunch time and early afternoon when temperatures will be at their highest.
2. Locate the deeper water
Cold water sinks so on larger stillwaters, such as reservoirs and bigger lakes, head for the deeper spots to stand the best chance of finding the fish which have headed there to cool down. On reservoirs, dam walls are often a good place to try, as the water is often very deep in these areas. Look out for steep banks around the lake, as these are often a sign that the water nearby will be deeper too.
3. Find moving water
Water movement agitates the surface and can drive off carbon dioxide and let in oxygen, which makes trout feel much happier. Find moving water and you'll often find fish. Aerators are a good place to try if you're fishing a small stillwater, but flowing inlets and cascades (like the one at Foremark Reservoir, shown above) also bring in cool, fresh water where trout congregate.
4. Fish deep
As trout go to cooler better oxygenated water in deeper parts of lakes and reservoirs when the weather is hot, you'll increase your chances of catching fish if you ensure you fish deep. Use a sinking line, such as a Di3, Di5 or even a Di7, to help get your flies deep quickly. If you don't have a sinking line, you can fish very deep by using a longer leader and straight-lining or using an indicator.
5. Avoid small stillwaters
Small stillwaters are shallower and more prone to warming up. These low oxygen conditions stress fish and puts trout off the feed and make them lethargic and reluctant to take a fly. Sometimes it can even impact the health of the fish, as trout like cool, well oxygenated water, not warm low oxygen water. Things get so tough at many small stillwater fly fisheries that some choose to shut for the summer instead. Your best bet would be to avoid small stillwaters completely if you can and return when temperatures drop.
6. Head for the hills
Upland fisheries, especially reservoirs, located up in the hills can be cooler than small stillwater fly fisheries during the summer months. Your chances of catching trout here will be higher, but it still won't be easy.
7. Fish static
Warm, low oxygen water means fish are less active and won't be as keen to chase a fly as they are when the temperature is lower and the water is saturated with oxygen. Instead of pulling lures, slow everything down as much as you can and fish with a slow figure eight retrieve, or fish completely static. Straight-lining buzzers, blobs and nymphs can work well, as can suspending a wide range of fly patterns deep below a strike indicator.
8. Try the river
While river fishing can be just as tricky when temperatures are high, at least the water is usually a bit colder and better oxygenated. If you have the choice, you might be better off picking the river over your usual stillwater trout fishery if you want to be in with a better chance of catching a trout during a heatwave. Stay late and the fishing could actually be pretty good.
9. Target other species
While trout can be very tough to catch when it is hot and sunny, many coarse fish species will be much happier to take a fly. While you should definitely avoid targeting pike on the fly in summer (which can experience oxygen stress and could suffer), perch, rudd, roach and carp all love to take flies too and are great fun on a fly rod. Rudd and roach love dry flies, while perch are partially to slowly fished nymphs. Carp can be trickier, but baiting with dog biscuits and fishing deer hair carp flies can get you into the fish. If you're near the sea, mullet, bass, pollack and mackerel are well worth targeting.
10. Help fish recover after a fight
As the fight can increase a fish's requirement for oxygen, and as warm water holds less of it, they can struggle to catch their breath when released. Unhook in the water and try not to remove the fish to improve fish welfare if you're fishing catch and release. Hold the fish upright in the water until it's fully recovered and allow it plenty of time to rest before letting it go.