Myths, lies, and old wives’ tales loom large in the outdoor pursuits. Here at MeatEater, we’re dedicated to separating facts from bullsh*t, so we created this series to examine suspect yarns. If there’s a belief, rumor, or long-held assumption you’d like us to fact check, drop us a note at factchecker@themeateater.com

Claim
Fish are more likely to bite when it’s raining.

Origin
I’ve been asked whether this is true more times than I can count. This yarn may have originated with dads trying to convince kids to stay out on the lake a little longer, but my own observations seem to corroborate the story.

A few years ago, my own dad and I did a three-day muskie trip in Wisconsin, floating a dozen miles of river every day. It rained one time for about a half-hour. My dad caught a 40-inch muskie on topwater right as the rain began, and another, slightly larger one right as the rain ended—the only two muskies we caught that entire trip. Seeing is believing, and numerous other examples from my lifetime on the water have me convinced.

Still, I can’t help but wonder whether the tired adage about fishing in the rain is grossly oversimplified. Could the pitter-patter of droplets on the surface cause fish to perk up? Or are there other, more important factors at play. My own personal hunch is that the cloud cover and drop in barometric pressure that come along with rain play a bigger role in fish activity than rain itself. A great many anglers believe that cloudy skies and/or a falling barometer signal good fishing.

Facts
To check my suspicions, I called up my friend and fisheries biologist John McMillan. Widely considered one of the top trout, salmon, and steelhead researchers in the country, John now serves as the science director for Trout Unlimited’s wild steelhead initiative after many years with the NOAA. He’s also one of the most talented and knowledgeable fishermen I know.

McMillan says that any angler paying any attention will notice that fishing is usually better during rainy or cloudy weather. The reasons for this aren’t entirely clear, but he suspects that it has something to do with how juvenile fish respond to rain.

“When rain comes, the fish become much more surface oriented,” McMillan said. “I think so much of this stems from when it’s raining, for a juvenile fish, that’s the time when the birds just tend to go sit in the trees and stop feeding, they don’t have to worry about kingfishers and mergansers as much. Some of the insects [hatches] start to go crazy too. The fish feel safe. It’s like the cloud cover is providing them a respite from predation and an opportunity to eat.”

McMillan suspects that adult fish may retain a lingering affinity for rain and clouds. And for the fish-eating ones among them, it’s an opportunity to take advantage of the juvenile fish moving around in open water. He also said that the onset of rain means that the barometric pressure is dropping, another sign of good fishing many anglers look for.

“I think what the barometer is telling them basically is that a storm is coming and when the storm comes, you don’t know how long that storm is going to put the river out to make it very difficult for you to feed and get food,” McMillan said. “It’d be like us if we knew the coronavirus was coming three months earlier, we would have prepped, right? We would have stockpiled food and toilet paper and all that stuff. The fish are just trying to get as much food as they can because they don’t know how long that shitty period is going to last.”

McMillan said that the effects of barometric pressure on fish physiology has not been sufficiently studied and is thus not well understood. It would probably require a pressurized chamber to rule out other factors. Many researchers and anglers postulate that fish become more active during a falling barometer because it is relieving pressure on their swim bladder and they can move about more freely. McMillan likens this to the sensation of popping your ears to pressurize in an airplane. But then other folks point to the fact that halibut fishing often turns on during falling pressure, but halibut don’t have swim bladders. Regardless of the mechanics, ask most any serious angler and they’ll tell you fishing is better during low or falling pressure—which often correlates with rain, but usually occurs well before the rain begins.

But none of this is to say that the raindrops falling on your head and your waterway have no direct effect. Rain could also contribute to increased fish activity by aerating and cooling the water during times of low dissolved oxygen levels in the summer. It can also increase turbidity (a fancy word for murkiness) and wash insects and other fish food off the banks. This may not always be true, however. Rain during cold weather can also serve to drop the water temperature and send fish into lockjaw. 

Takeaway
Yes, fishing is often better than normal when it’s raining, but it may not be the rain itself causing the hot bite. Pay attention to as many factors as you can. But above all, don’t let a little precipitation prevent you from going out or staying out on the water. The best time to go fishing is when you have time to go fishing. You never know what you might be missing.

Sources
Interview with John McMillan

Rain-driven changes in fish dynamics: a switch from spatial to temporal segregation by Nicholas L. Payne et. al — Inter-Research Science Publisher

Movement Patterns of Adult Black Crappie, Pomoxis nigromaculatus, in Brant Lake, South Dakota by Christopher S. Guy, Robert M. Neumann, and David W. Willis — Journal of Freshwater Ecology

Fishing by the Barometer by George Poveromo — Weather.com

How Rain Affects Your Fishing — Mepps Tackle

Feature image by Tosh Brown.