These maps show where each climate state tends to leave its mark on winter precipitation across North America. Pick an ENSO state (La Niña, neutral or El Niño, classified by the Relative Oceanic Niño Index, RONI) and/or a phase of the Madden-Julian Oscillation (MJO), and the map averages every matching day in the 1979–2026 record against the climatological normal for that season.

Precipitation is shown as percent of normal over land in the lower 48, from ERA5-Land reanalysis on a 1° grid. Atmospheric river frequency is the share of days with an atmospheric river (integrated vapor transport of at least 250 kg/m/s) compared with the normal rate, from ERA5 over North America. Stippling marks grid cells whose signal passes a 95% significance test, adjusted for day-to-day autocorrelation. Read coherent patches of stippling rather than single cells.

ENSO composites carry the most robust signal for California and the Sierra Nevada. MJO composites are noisier, and the MJO's atmospheric river signal lags its phase by roughly a week. For custom filters and lead times, use the Pattern Heatmaps; for county-level temperature and precipitation by any mix of drivers, the Analog Builder.