The 2004 North Indian Ocean cyclone season had no bounds, but cyclones tend to form between April and December, with peaks in May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean.
In 2004, RSMC New Delhi identified one Very Severe Cyclonic Storm and three Severe Cyclonic Storms. Out of the four cyclonic storms, three developed over the Arabian Sea and only one formed over the Bay of Bengal. Joint Typhoon Warning Center identified one more tropical cyclones(4A) in Arabian sea. The notable features is that the Arabian sea was more active than the Bay of Bengal during 2004.
The Arabian sea severe cyclone “Agni” in November formed very close to the equator near latitude 1.5N. Cyclogenesis over the north Indian Ocean at such low latitudes has not occurred in the past. The coexistence of cyclonic disturbances over the Arabian sea and the Bay of Bengal as occurred in June 2004 is also not common. This had however helped the progress of the southwest monsoon across the country during the onset phase.
This was the first North Indian season that featured the naming of storms, though only two storms received names.
On May 5, Tropical Depression 1A developed in the Arabian Sea, 200 miles (320 km) west of the Indian coast. It wandered for the next three days, slowly strengthening to its peak of 50 mph (80 km/h) winds. The tropical storm turned northwestward, where dry air and moderate shear caused the system to dissipate on the 10th.
Since the storm remained over water throughout its existence, the heaviest rainfall produced by the cyclone fell over water. However, in parts of Gujarat, upwards of 225 mm (8.9 in) of rain fell, triggering flash flooding. At least five people were killed in relation to ARB 01 in India. Amini Divi in Lakshwadeep Islands recorded 1168 mm rainfall on May 6, 2004 and created a record for the north Indian ocean rainfall from an cyclone. It was associated with the passage of tropical cyclone and recorded 1840 mm rainfall during just three days viz. May 5–7, 2004 
A tropical storm formed on May 17 in the Bay of Bengal, 230 nautical miles (430 km) south of Calcutta. It drifted southwestward initially, followed by a turn to the northeast where it intensified to a 70 mph (110 km/h) tropical storm. Not long after on the 19th, the tropical storm hit Myanmar, and dissipated later that day. Within hours of making landfall, the IMD reported that the system rapidly intensified, attaining peak winds of 165 km/h (105 mph) and a minimum pressure of 952 mbar as it moved onshore. The storm caused heavy flooding and damage, amounting to 220 casualties.
On October 1, a tropical depression developed in the northeastern Arabian Sea. It moved northeastward, where it strengthened into a tropical storm on the 2nd. The name, "Onil" was the first cyclonic system to ever be named in history of the North Indian Ocean cyclones. Onil later reached a peak with sustained winds of 45 mph (72 km/h), though other forecasting agencies estimated a stronger storm. Regardless, the storm entrained dry air and rapidly weakened. Though operationally Onil was said to have made landfall on India, the low level circulation halted just before landfall, drifted southward, and dissipated on the 10th.
In the post-analysis by RSMC New Delhi, the system weakened into a depression over Gujarat-Kutch coast in the evening of 3 October without crossing the coast.
On November 19, an area of convection developed and persisted about 500 miles (800 km) east-southeast of Colombo. Under an area of moderate vertical shear, it moved west-southwestward and slowly organized. It nearly dissipated on the 24th, but redeveloped on the 26th under an area of favorable upper level winds and good diffluence aloft. On November 27, it became Tropical Depression 5A, and after moving to the west-southwest, became Tropical Storm Agni on the 28th only 50 miles (80 km) from the equator (about 0.7°N). In its developmental stages, its circulation crossed the equator briefly into the southern hemisphere, while retaining its counter-clockwise spin. Under unusually favorable conditions so close to the equator, Agni strengthened and turned to the northwest. The convection concentrated, and quickly became a cyclone on November 29. A pinhole eye briefly developed, but dry air and vertical wind shear weakened Agni back to a tropical storm. The effects were temporary, and Agni re-attained cyclone status on the 30th. On December 1, the shear and dry air returned, and Agni again weakened back to a tropical storm. After moving to the northwest for much of its lifetime, the storm turned to the west towards northeastern Africa, under the influence of the subtropical ridge to its north. Late on December 3, the storm weakened to a tropical depression, and made landfall on eastern Somalia on the 4th. It turned to the south, and dissipated after reaching the Arabian Sea on December 5.
When Tropical Storm Agni reached a position of 50 miles (80 km) north of the equator, it became the nearest a tropical cyclone has ever approached to the equator, less than half of Typhoon Vamei's previous record distance of 103 miles (166 km). However, because Agni formed more to the north and tracked southwestward, Vamei retains the record for the southernmost formation. RSMC New Delhi also admitted that cyclogenesis over the north Indian Ocean at such low latitudes has not occurred in the past. Because the storm was weak and the convection disorganized when it hit Somalia, no damage or deaths were reported from the storm.