Heavy and extreme rainfall in Makkah Region of Saudi Arabia at the present climate

In recent decades, the frequency and intensity of rainfall have increased in the Makkah region of western Saudi Arabia, leading to flash floods. The sparse network of surface observation stations is inadequate to fully capture the rainfall dynamics in the area, highlighting the need to use more densely distributed rain gauge datasets. Consequently, this study examines heavy to extremely heavy and extreme rainfall in the Makkah region using data from three manned stations located in Jeddah, Makkah, and Taif, for the time period from 1985 to 2023, along with data from 24 automatic weather stations (AWSs), most of which have been operational since 2014. The rainfall is categorized into heavy (10 ≤ RF < 20 mm), very heavy (20 ≤ RF < 30 mm), and extremely heavy (RF ≥ 30 mm) while extremes are very wet (95th percentile) and extremely wet (99th percentile) days. Jeddah experienced 72 heavy to extremely heavy and 10 extreme rainfall days, with the highest occurrences in November. Makkah (Taif) recorded 139 (196) heavy to extremely heavy and 20 (36) extreme rainfall days, peaking in November (April). Rainfall increased at rates of 21.22, 35.37, and 38.94 mm per decade for Jeddah, Makkah, and Taif, respectively, during the latter half of the study period. AWS data revealed the daily highest rainfall 182.0 mm at Jeddah Janub in November 2022 followed by 143.4 mm at Taif Al Kor in August 2021, and 109.0 mm at Makkah Al Jamoum in November 2020. AWS data also confirmed that heavy and extreme rainfall was most frequent in November in Jeddah and Makkah, while April and November in Taif. Therefore, intense rainfall poses potential flash-flood risks in the region. Further research using radar, satellite, and climate models is recommended for improved flood management and disaster planning of the region.