Increasing negative impacts of high temperature on cotton production during the flowering and boll-setting in the context of global warming

High-temperature exposure (HTE) during the flowering and boll-setting stage is an important climatic constraint on cotton production, but its probabilistic effects on yield and fibre quality are not well understood. Meteorological records and county-level cotton yield data from 1990 to 2022 were integrated with fibre-quality observations from 843 monitoring sites during 2016–2022. Copula models were used to quantify yield and quality probabilities under HTE, while an equal-weight ensemble of nine Coupled Model Intercomparison Project Phase 6 (CMIP6) global climate models was used to project future HTE under SSP1–2.6, SSP3–7.0, and SSP5–8.5. From 1990–2022, cumulative HTE days increased in 69.01% of cotton-growing regions, with significant increases observed in 19.72% of the regions. During 2016–2022, inferior cotton grade, micronaire, and fibre strength occurred at 32.50%, 16.84%, and 19.10% of monitoring sites, respectively. HTE increased inferior strength and micronaire risks in southern Xinjiang but grade deterioration risk in northern Xinjiang. Increasing HTE days raised the probability of lower fibre-strength grades by up to 44% and yield reduction by up to 18%. Multi-model projections indicate a marked shift toward longer-lasting HTEs by 2051–2100, particularly under SSP3–7.0 and SSP5–8.5. Future yield-loss risk generally increased, whereas several fibre-quality indicators remained stable or shifted toward more favourable grades in some regions. These findings support region-specific adaptation for climate-resilient cotton production in arid Xinjiang.