El Niño Could Delay Chicago's Peak Fall Colors This Year, Arboretum Says
Lisle, Ill. – September 22, 2026 -- Scientists at The Morton Arboretum are tracking how a strengthening El Niño could push back peak fall foliage across the Chicago region this year, potentially compressing the color season into a shorter, more intense stretch in late autumn.
Summer weather extremes are already scrambling normal leaf-color timing
Christy Rollinson, Ph.D., senior scientist in forest ecology at the Arboretum, said this summer's swing from drought to heavy rainfall will affect trees unevenly across the region. Early-season drought typically triggers earlier fall color, and some early turners like the autumn blaze maple have already begun changing in late August and early September, particularly in high-stress spots like parking lots. But the Illinois State Climatology Office recorded significantly above-average precipitation over the last 90 days, offsetting that early drought stress.