Short answer: nobody knows, because nobody has measured it. We could find no study that compares striped bass feeding, or catches, in ordinary rain against dry weather. What has been measured sits at the two ends of the question: a flood big enough to send tagged bass out of a river, and young river herring that leave their home streams in pulses that rain and rising water can set off.
(If you meant rain bait: that is bay anchovy, nicknamed for the way a school dimples the surface like falling rain. Different question.)
What a flood did
Tropical Storm Irene came ashore at New York City on August 28, 2011, and Tropical Storm Lee followed just over a week later. The storms brought record rainfall, and the Hudson's flow at the Green Island gauge went off the chart:
| Hudson River at Green Island | Daily mean flow |
|---|---|
| August average, 2002–2012 | 269 m³/s (about 9,500 cfs) |
| August 29, 2011, after Irene | 4,471 m³/s (about 158,000 cfs) |
| September 8, 2011, after Lee | 3,028 m³/s (about 107,000 cfs) |
Helen Bailey and David Secor estimated currents of up to 2 meters a second at that gauge, close to 4 knots. Down the estuary the water rose and turned colder, fresher and lower in oxygen.
They had 75 striped bass tagged in the Hudson and New York Harbor in 2009 and 2010, roughly 16 to 39 inches (40 to 100 cm). Twenty-two of the 75 had working tags in the river or harbor through the storm weeks, and the authors compared those tracks with the same weeks of 2010.
The fish went south. Those up the river tended to run downstream and out to the coast; those in the harbor either stayed or left and headed south. In 2010 the tagged fish had drifted south too, but far less. Three fish were heard at the same receivers, or close by, right through the storms. Holding against the peak flow would have taken them 2.8 to 4.2 body lengths a second; the best sustained striped bass speed on record is 2.9 to 3.3, for 30 to 45 minutes. The authors think they may have found shelter.
The return took months. Harbor use in October 2011 fell well below October
- Three fish came back for short visits in late October and November,
possibly scouting, and two upriver fish eventually went back up the Hudson. Many lower-estuary fish stayed on the coast.
That is the one storm-scale measurement of striped bass and runoff we found, and its direction is leaving. It is also a flood, more than 16 times normal flow, and it says nothing about whether fish fed while the rain fell. Storms that come as wind and surf are their own story.
The long record is about seasons
The longest dataset that touches rain is from California, where striped bass were introduced in 1879. Over 42 years and 307,727 adult fish in the San Francisco Bay–Delta, Pascale Goertler and colleagues found the spring spawning run moved upriver later in years with more freshwater outflow, and later when the ocean was cooler; they think ocean temperature is the likely cue. That is a shift in the calendar between years, not a rainy Saturday.
Where rain moves something: the bait
The clearest rain effect on record is on prey. Young alewives leave the water where they hatched as it cools, from late summer into early winter depending on where. Karen Greene and colleagues' 2009 habitat review for the Atlantic States Marine Fisheries Commission collects what sets them moving: changes in flow, water level, rain and light.
The shape is the useful part. In a Rhode Island drainage, 60 to 80 percent of a season's young alewives left on about 8 percent of the available days, in waves of two or three days, and how many left had nothing to do with how big the change was. A 1961 thesis found 98 percent of juveniles left after periods of heavy rain, and a Massachusetts one, on the Parker River, found departures set off by a rise in flow. But extremely high flow may work against it: in the lab, young alewives avoided currents faster than 10 cm a second, about a fifth of a knot. Some researchers give water temperature and dark nights the main role.
The adults' spring run is less tidy. Henry Legett and colleagues read 8 to 28 years of daily counts at 12 Massachusetts herring runs. Streamflow never predicted whether herring were running, and predicted how many in only 2 of the 12, in opposite directions: more flow meant more fish in the Agawam and fewer in the Monument, on the Cape Cod Canal. Water temperature was the consistent signal.
So rain can move young herring out of some streams, in pulses, late in the season. Whether striped bass gather for those pulses has not been measured either.
Who is out in the rain
Fishing reports cannot settle it, because rain changes who goes. Stephen Midway and Paul Miller matched seven years of weekly fishing effort on the Louisiana coast to the weather: rain cut effort in 3 of 12 months in one region and 4 of 12 in the other. Those are Gulf anglers, but the point carries. A rainy-day report comes from fewer, more committed people, and tells you about them as much as about the fish.
What to do with it
This part is inference.
Don't stay home for the rain, and don't go because of it. Nothing measured says it helps or hurts. Thunder is a reason to leave the water; drizzle isn't.
Runoff needs a river to arrive. On the sandy upper Cape, a U.S. Geological Survey study found surface runoff negligible: rain that does not evaporate soaks into the aquifer instead of running off. An open beach with no creek gives a shower little to deliver. If runoff turns your water brown, that is the dirty-water argument.
In late summer and fall, check the herring streams after rain. When a rain lifts a stream with young herring above it, the mouth is worth a look over the next few days. Expect pulses, and don't expect a bigger rain to mean a bigger one; a true flood may stop it.
After a real flood, look outside the river. In the one flood anyone tracked, the fish left for open water and took months to come back.
How StripedLines uses this
StripedLines is built for striped bass. It makes no claim about what rain will do at a particular mouth; the research above does not size it. Its rating ranks places against each other. It is never a chance of catching.