Fly Fishing the South Platte in the Rain
Rain changes everything on the South Platte — what it does to the fish, which hatches it triggers, and how to dress and fish when the weather turns.
Most fly fishers leave when it rains. I’ve watched it happen a hundred times at Cheesman Canyon — the first drizzle hits and the parking lot clears out like someone yelled fire. Me? I’m still fumbling with my rain hood, half-soaked and grinning, because by the time I’ve rigged up I usually have a mile of productive water all to myself.
Rain on the South Platte isn’t a problem. In most cases, it’s an advantage — and the guys driving home are doing you a favor.
What Rain Does to the Fishing
BWO hatches: Blue-wing olives are triggered by overcast, cool, humid conditions. They don’t like bright sun. A gray, rainy October or April afternoon on the South Platte is the best BWO hatch condition you’ll find. The fall BWO season guide covers how to fish these conditions for maximum effect. The rain keeps insects on the water longer and the fish feed confidently under low light without the overhead pressure of direct sunlight.
I’ve had my best Baetis fishing on days that started with drizzle at 9 AM. The hatch came off heavy by 11 AM and continued until 2 PM — three hours of rising fish in a section of Cheesman that had zero competition from other anglers.
Reduced surface pressure: Fish that are spooky in bright conditions become bolder under clouds and rain. The light penetration drops, the overhead predator threat diminishes (eagles and ospreys don’t hunt effectively in rain), and fish move from holding cover into feeding positions more aggressively. Fish you couldn’t approach in bright afternoon sun at Deckers are approachable in rain.
Reduced angling pressure: This is the most consistent benefit. A rainy Saturday morning means I have Cheesman mostly to myself. The beats that hold five anglers on a bluebird day hold one or two in rain. If your South Platte fishing happens on weekends when pressure is high, checking the forecast and picking a wet day for your trips is a legitimate strategy.
When Rain Is a Problem
Not all rain is fishing weather. The scenarios that actually force you off the water:
Heavy rain + runoff: A significant thunderstorm in the upper watershed can push the South Platte into unfishable flows within a few hours. Colorado’s Front Range afternoon thunderstorms in July and August can dump 1–2 inches on the mountains above Cheesman and blow the river out by 4 PM. Watch the radar, not just the weather at the river.
Lightning: The South Platte canyon sections have minimal tree cover and put you in the open with a graphite rod. Colorado summer lightning is a genuine threat. When the storms build and lightning starts, get off the water. This isn’t cautious advice — it’s just common sense. I’ve gotten caught in fast-moving afternoon storms at Cheesman twice. Both times, I hiked out early. The fishing can wait.
Runoff from local storms: A concentrated storm directly over the Deckers watershed — even without affecting the upstream sections — can add turbid runoff from the hillsides and small drainages into the river within an hour. Clear water goes off-color fast in localized storms. If the river suddenly colors up, it’s time to change tactics (bigger nymphs, streamers, edges) or call the day.
Is rain good for fly fishing the South Platte?
Usually, yes. Overcast, rainy conditions trigger BWO hatches, drop the light penetration so spooky fish feed more boldly, and clear the crowds off the water. The exceptions are heavy runoff that blows the river out and lightning — both of which send you home.
Rain Gear That Actually Works
Here’s where I’ll admit a bias: I have strong feelings about rain gear, mostly learned the hard way. Wading in the rain requires waterproof gear that works when wet for eight hours, not forty-five minutes.
Wading jacket: The one piece of gear I won’t compromise on. A proper waterproof-breathable wading jacket with sealed seams and a DWR treatment keeps you dry in rain that would soak through a standard rain jacket in two hours. Simms, Patagonia, and Skwala all make legitimate wading jackets. A cheap rain jacket from a box store is not the same thing — the breathability fails when it’s wet from both sides (rain outside, body heat inside) and you end up soaked in condensation.
Fleece base layer: The South Platte in October rain is cold. A Merino or fleece midlayer under the wading jacket keeps you functional in 45°F air and 42°F water. Cotton is not an option in cold rain — it loses all insulation value when wet.
Waterproof gloves: Optional in mild rain, necessary in cold October or November rain. I fish with fingerless fleece gloves in cold rain and switch to full waterproof gloves when air temperatures drop below 40°F. Cold hands are the fastest path to a shortened day.
Tactics in Rain
Match the BWO hatch when it comes off. A size 18–22 BWO emerger or cripple is the pattern during overcast Baetis conditions. If you see fish rising in rain, your first response should be a BWO pattern. Parachute BWOs, RS2 emergers, and Barr’s Emerger are the three I reach for first.
Fish the surface longer. Overcast conditions mean fish hold in feeding position longer — they’re not pushed back to holding lies by sunlight and pressure. A feeding fish in bright sun has a 2–4 foot lane it covers before retreating. In rain and cloud cover, that same fish may cover 10–15 feet consistently. More time in the zone means more opportunities.
Switch to large nymphs when rain hits. If rain is muddying the water slightly, a size 12–14 stonefly nymph or large hare’s ear is visible at greater depths and triggers strikes in conditions where a size 20 midge is invisible. The fish can still feel the pressure wave of a large nymph in off-color conditions.
The river in rain is yours. Most of the competition has driven home already. Pack quality waterproof gear, check the radar before your drive, and don’t let a gray sky talk you out of a day on the water. The South Platte hatch calendar shows the BWO windows across all sections — plan your rainy-day trip around those dates for the best surface fishing of the year.
Worst case, you stay dry and catch nothing. Best case, you’ve got a canyon full of confident fish and not a soul to share it with. I’ll take those odds every time.