Heavy rains have delayed more than 100 flights and caused the cancellation of over 170 others at a major airport in Guangzhou, capital of south China's Guangdong Province, airport authorities said Sunday. According to the Baiyun International Airport, nearly 103 flights were delayed and 101 departing flights and 72 inbound ones were canceled due to thunder and rain, which has stranded thousands of travellers as of 06:40 p.m.. The meteorological bureau of Guangdong said rainstorm and hail hit Guangzhou in the morning. Airport authorities issued a red rainstorm alert at 12:30 p.m. on Sunday. China has a four-tier rainstorm alert system, with red being the most serious, followed by orange, yellow and blue. The airport and airlines were ready to provide emergency services to passengers.