This study presents the first daily-resolution assessment of solar attenuation mechanisms across Iraq's climatic gradient using five years of ground-based observations (2020–2024) from the Iraqi Meteorological Organization and Seismology. Six novel analyses are applied to data from Basrah, Baghdad, Mosul, and Sulaymaniyah: extreme event characterisation, composite recovery curves, dust–rainfall separation via diffuse fraction validation, viable solar season length, rainfall intensity breakpoints, and daily Weibull wind fitting. Results reveal a pronounced north–south dichotomy: southern arid zones experience dust-dominated attenuation with rapid 1–2 day recovery, while northern Mediterranean zones face rainfall-driven suppression requiring 3–5 days storage autonomy. Diffuse fraction analysis confirms dust days elevate scattering to 0.48–0.56 (ΔDF = +0.27–0.31 vs. clear), mechanistically distinct from rain events (DF > 0.60). Wind–solar correlations are uniformly positive (r = +0.21 to +0.36, p < 0.001), refuting complementarity and confirming synchronous summer peaking via shamal circulation. Rainfall thresholds for 50% irradiance loss range from 6.8 mm/day (Basrah) to 9.2 mm/day (Mosul), directly informing battery autonomy sizing. A representative 10 kWh/day load requires 28.8 kWh storage in Basrah versus 71.9 kWh in northern cities. Daily Weibull fitting identifies Basrah as the only marginally viable wind site (92.8 W/m²). These findings establish a daily-resolution design framework for renewable integration in arid climates, demonstrating that climate-zone-specific battery storage, not wind hybridization is critical for winter grid reliability.