Decreased aquifer water in the Texas High Plains has increased the risks associated with irrigation, including lower irrigation volume and the need to balance seasonal water demands among crops, requiring management of both irrigation rate and timing. Boll distribution measurements in cotton (Gossypium hirsutum L.) can be used to quantify the effects of irrigation on productivity and were used in a study of irrigation rate × timing from 2011 to 2013 in Halfway, TX. Field experiments quantified cotton boll distribution using three in-season irrigation levels (maximums of 0, 3.2, and 6.4 mm d–1) during three different irrigation periods determined by accumulated growing degree days (GDD) based on the threshold of 15.6°C: period 1 (P1, <525 GDD), period 2 (P2, 525–750 GDD), and period 3 (P3, >750 GDD). Combinations of these factors resulted in 27 irrigation treatments, applied with a low energy precision application (LEPA) pivot. Heavy irrigation early in the growing season used more water, did not increase boll number, and was often detrimental to yield. Mid- and late-season irrigation improved yield and fiber quality, with P2 irrigation influencing yield in the middle of the plant and P3 irrigation controlling yield at the top of the plant. Moderate irrigation later in the season minimized effects of short-term water deficit observed in other similar studies. These results provide insight into optimizing cotton water use in a region with declining crop water availability, increased pumping restrictions, and a challenging climate.