One reason that led to the British decision to attack Baltimore and not send the fleet north to Rhode Island as contemplated, then to return, was the annual autumn weather cycle of the equinoctial storm systems. These mid-Atlantic seasonal patterns along the coast played an integral role in the British strategy during their occupation of the Chesapeake. Now, it certainly became a factor in Vice-Admiral Alexander Cochrane’s decision to attack Baltimore and their subsequent raids in southern Maryland and Virginia in October before departing the Chesapeake.
In the early 19th century equinoctial storms were often referred to as heavy rain storms that occurred near the autumnal equinox (Sept. 22) in the Northern Hemisphere. This commonly used term has been replaced by the Lesser Antilles Carib word “hurricane” even though hurricanes are known to occur in the Northern Hemisphere as early as June and as late as November. When the British withdrew from Washington a severe squall line of intense thunderstorms struck, often inaccurately referred to as a hurricane that doused the flames of the city.
In Septmber 1814 Admiral Cochrane informed the First Secretary of the Admiralty in London, John W. Croker one of his reasons for attacking Baltimore: “…the approaching equinoctial new moon rendering it unsafe to proceed immediately out of the Chesapeake with the combined expedition, to act upon the plans which had been concerted previous to the departure of [HMS] Iphigenia; Major General [Robert Ross] and myself [have] resolved to occupy the intermediate time to advantage, by making a demonstration upon the city of Baltimore…”
During the Battle for Baltimore, such a thunderstorm made its appearance on September 13-14, 1814 when they augmented the flash of bombs and rockets that added to the grandeur and terror of the naval bombardment of Fort McHenry.
Sources: Dr. Kent Mountford, Estuarine Ecologist and Environmental Historian to the author on an investigation of weather patterns mentioned in Admiral Cochrane’s letter of September 17, 1814; Admiral Cochrane to Secretary Croker, H.M. ship-of-the-line Tonnant, Chesapeake, September 17, 1814. Printed in The Naval War of 1812: A Documentary History, vol. 3, (Washington, Naval Historical Center), 289-290; “Joseph Hopper Nicholson: Citizen Soldier of Maryland,” by Scott S. Sheads (Baltimore: Maryland Historical Magazine, vol. 98, No. 2,Summer 2003), 133-151.