The Weather on June 17, 1775: The Battle of Bunker Hill

Contributed by Dr. William Minsinger, President Emeritus, BHOSC

Contemporary map of Charlestown and the area around Bunker Hill and Breed’s Hill. Image from NPS.gov.

America’s 250^th birthday – its semi-quincentennial – is a good opportunity to take a step back in time to look at the weather on June 17^th, 1775, during the pivotal Battle of Bunker Hill. The British in their bloody retreat through Charlestown from Lexington and Concord had built a small redoubt on Bunker Hill but British General Thomas Gage withdrew his troops back to Boston. Colonial General Artemus Ward was trying to form an army out of the large group of patriots stationed in Cambridge and other locations surrounding Boston – these men had responded to the call to arms after Lexington and Concord. To challenge the British, he ordered Colonel William Prescott to take a force of about 1,000 men and build a redoubt on Bunker Hill. Heading out on the night of June 16^th, Prescott and his men bypassed Bunker Hill and fortified the lower Breed’s Hill – a direct challenge to the British bottled up in Boston. The Americans continued to fortify as General Gage recognized the need to respond to this challenge and quickly conceived plans to land a large force to retake Bunker Hill and Breed’s Hill. The weather that day has been debated with some historians in the 19^th century saying it was one of the hottest days in memory. However, David Ludlum – longtime editor of Weatherwise and AMS historian – wrote (Ludlam, 1984) that these historians overlooked the weather records of both Harvard Professor Winthrop, who had relocated to Andover, and Dr. Holyoke in Salem. By reconstructing their observations Ludlum deduced that a cold front with some rain had passed on June 14^th followed by pleasant weather suggesting that the temperature was warm but not hot for the season, By June 17^th a high pressure system probably crested over New England – the morning temperature was 61 degrees F in Andover rising to 80 degrees F sometime in the afternoon at the height of the battle. It must be remembered that the sun with clear skies was just a few days from the summer solstice making the day feel even warmer. Ludlum noted that the wind was shifting into the SW bringing in more humid air by the hour on that day. The British disembarked at Morton’s Point and stopped to eat their rations thinking they would easily outflank the redoubt and take it from the rear. However, Colonel John Stark with his New Hampshire regiment was coming on the field to extend the American lines to the Mystic River where his troops threw up a stone wall on the beach and reinforced a fence line. As the British approached the Americans fired from three ranks stopping the flanking move. Two frontal assaults proved very deadly for the British as they marched over a pasture with knee high hay, stone walls. and fences slowing their advance uphill. The heat of the day however can be surmised by what happened on the third and final charge up the hill – the British who proudly wore their packs and red wool uniforms into every battle dropped their packs and even were ordered to remove their red coats and make a bayonet charge which proved successful in taking the redoubt where the Americans were running out of gun powder. The battle devolved into hand-to-hand combat and General Joseph Warren and many of the Americans were killed defending the redoubt. Colonial losses were estimated to be 450 soldiers, while British losses were over 1000.

Painting by John Trumbull, The Death of General Warren at the Battle of Bunker’s Hill, June 17, 1775 (1786), currently in the collection of the Museum of Fine Arts, Boston. Public domain Image.

The Battle of Bunker Hill will be long remembered as a very hot battle – fought on a hot day. David Ludlum reminds us however that the next day had a higher maximum temperature of 91 degrees F as the high pressure moved off the coast and southerly winds brought in very warm and humid air – perhaps leading to the idea of exceptional heat. The true lasting impact of the battle was to give confidence to the Americans that they could stand up to the vaunted British regulars and gave pause to the British who suffered nearly 50 percent losses with many of their officers being killed. General William Howe, the British commander at Bunker Hill, was thereafter always reluctant to attack entrenched Americans in frontal attacks and General Gage remained penned up in Boston until the British departed the city in March 1776. References