San Juan midges and caddis building as Rio Grande holds low and clear

What's Biting

What's Next

**Conditions over the next 2–3 days:** We're working from a single data point — the Rio Grande at USGS gauge 08330000 came in at 54.2 cfs just before dawn on May 10. If flows remain in that range rather than spiking with late snowmelt, the gorge section near Taos should hold low, fishable clarity through the weekend. Watch for afternoon warming: as air temps push into the mid-60s, subsurface nymph activity typically gives way to hatch-triggered surface feeding on both rivers.

The San Juan tailwater near Navajo Dam is regulated and far less sensitive to upstream runoff swings. Flows there should remain consistent. MidCurrent this week highlighted midge patterns as the standout tactic for clear, pressured tailrace water — on the San Juan, that translates to Size 22–26 zebra midges and RS2s on 6X or 7X tippet in the upper catch-and-release section. Plan to fish light and slow.

Hatch Magazine recently covered caddis emergence patterns in tailwater contexts. Early May typically marks the window when Grannom and net-spinning caddis begin showing on Southwest tailwaters. On the San Juan, look for sporadic surface activity in the late afternoon — the 3 to 6 p.m. slot before evening cooling shuts things down is the prime window. An Elk Hair Caddis in Size 16–18 or a soft-hackle emerger fished in the surface film can be effective once fish begin rising.

**Weekend window:** If Rio Grande flows stay low and weekend daytime temps cooperate, Saturday and Sunday should offer good wade access throughout the gorge. Arrive early — afternoon winds are a consistent mid-May pattern in northern New Mexico and can make drag-free drifts difficult by midday. On the San Juan's catch-and-release section, weekend pressure builds early; arriving before 7 a.m. or targeting the post-hatch window after 4 p.m. can make a measurable difference in fish contact.

**One variable to watch:** Any late-season precipitation event or above-average warming mid-week could trigger a brief runoff pulse on the Rio Grande. The upper drainage can still shed snowpack into early June in above-average years. If the gauge at 08330000 climbs back above 200 cfs, the gorge section near Taos will likely cloud up temporarily — that's the signal to redirect effort to the San Juan, where Navajo Dam releases will keep conditions clear regardless of what the main river is doing upstream.

Context

In a typical year, the Rio Grande runs considerably higher through May — snowmelt from the mountains above Taos and the upper drainage can push flows well above 200 cfs as the season progresses toward its June peak. A reading of 54.2 cfs at USGS gauge 08330000 on May 10 suggests either a below-average snowpack year in the upper watershed or an early runoff pulse that has largely moved through. Neither scenario is unusual in northern New Mexico, where mountain snowpack has trended variable in recent decades, but it does mean anglers visiting the Rio Grande Gorge this season may be in a favorable clarity window — low, clear water before summer heat sets in can be genuinely productive for trout, even if fish density tends to run lower in dry years.

The San Juan River near Navajo Dam operates on a different seasonal clock. Its tailwater character buffers it from most snowmelt swings that affect the Rio Grande's freestone reaches. May is historically one of the stronger months on the San Juan — water temperatures settle into the productive range, hatches build toward peak summer biomass, and fish that have been feeding actively since April continue to put on condition ahead of summer.

There are no reports in this week's feeds that directly address New Mexico waters in 2026, which limits our ability to benchmark this season against prior years. What the broader national feeds do suggest is that late-spring trout patterns are tracking roughly on schedule across the West — MidCurrent reported midge rigs performing well in clear tailrace conditions, and Hatch Magazine addressed caddis emergence timing. Those signals, while not New Mexico-specific, indicate the Southwest tailwater window is open. The absence of direct NM intel this week is a reporting gap, not an indication that conditions have deteriorated.