The Summer That Killed Thousands
The summer of 1936 arrived on a landscape already devastated. The Great Plains were in their fifth year of severe drought. Topsoil that had survived for millennia was blowing off the land in the massive dust storms covered in earlier Weather Daily pieces. Farmers who hadn’t yet abandoned their land were watching crops fail for the fourth or fifth consecutive year. The Depression had stripped away economic reserves that might have cushioned the blow.
Into this already catastrophic situation came the heat. Beginning in late June and continuing through most of July and into August, a heat wave of extraordinary intensity and duration settled over the central United States and Canada. Temperature records that had stood for decades — some set during the scorching summer of 1934 — were shattered across state after state. An estimated 5,000 people died in the United States alone, with several thousand more deaths in Canada, making the Heat Wave of 1936 the deadliest heat-related disaster in North American history. Many of the temperature records set that summer still stand today, nearly 90 years later.
The Atmospheric Pattern
The heat wave of 1936 was produced by a persistent, large-scale atmospheric pattern that modern meteorologists would recognize as a blocking high — a dome of high pressure that settled over the central United States and refused to move for weeks at a time.
Under a blocking high, air subsides from the upper atmosphere toward the surface, warming as it descends through adiabatic compression — the same process that warms air moving down a mountain slope, but operating over a much larger area and altitude range. This subsiding, warming air suppresses cloud formation and precipitation, producing the clear, sunny skies that allow solar radiation to heat the surface without interruption. The stagnant air mass accumulates heat day after day with no frontal passage, no significant rain, and no relief from the oppressive temperatures that build over weeks.
The Dust Bowl conditions amplified the heat in a specific and devastating way. In a normal summer, evapotranspiration — the evaporation of soil moisture and the release of water vapor through plant leaves — acts as a natural cooling system across the landscape. Moisture evaporating from soil and vegetation absorbs heat from the surrounding air, moderating temperatures. Across the Great Plains in 1936, the soil was bare, dry, and depleted of moisture by years of drought. There was no soil moisture to evaporate and essentially no vegetation to transpire. The natural cooling system had been stripped away, leaving the surface to absorb solar radiation without the moderating influence that normal landscape conditions would provide.
The result was surface temperatures that exceeded anything the same atmospheric pattern would have produced over a non-drought landscape — a feedback loop in which the Dust Bowl drought made the heat wave more extreme, and the heat wave further stressed the already-devastated landscape.
The Records That Still Stand
The temperature records set during the summer of 1936 are among the most enduring in North American climate history. The persistence of these records nearly 90 years later is itself informative — it suggests that the combination of atmospheric pattern, drought conditions, and surface feedback that produced the 1936 heat was sufficiently extreme that comparable conditions have not recurred in the same locations since.
In Kansas, the all-time state temperature record of 121°F was set on July 24, 1936, at Alton — a reading that remains the highest reliably recorded temperature in Kansas history. North Dakota reached 121°F the same day at Steele — also still the state record. Oklahoma recorded 120°F at Tipton on August 10, 1936. Nebraska, South Dakota, and Indiana all set all-time state temperature records during the 1936 heat wave that remain unbroken.
Across Canada, the summer of 1936 was equally devastating. Manitoba set its all-time provincial temperature record in July 1936. Saskatchewan and Ontario also recorded extreme temperatures during the same period. The Canadian prairie provinces, sharing the same atmospheric pattern and the same drought-stripped landscape as the American Great Plains, experienced the heat with comparable intensity.
The concentration of all-time state and provincial records in a single summer is extraordinary from a climatological perspective. Heat waves are common. Heat waves that produce all-time temperature records across a dozen states simultaneously, records that then stand for nearly a century, reflect a convergence of atmospheric and surface conditions that has not been replicated in the subsequent decades — at least not yet.
Who Died and Why
The death toll of the 1936 heat wave — estimated at 5,000 in the United States, though the true number is likely higher due to incomplete historical record-keeping — was concentrated among specific populations and in specific conditions that illuminate the mechanisms of heat mortality with painful clarity.
The elderly were most vulnerable, as they are in every heat wave, for the physiological reasons covered in the senior pets weather piece that apply equally to older humans: reduced thermoregulatory capacity, diminished cardiovascular reserve, impaired thirst response, and reduced ability to recognize and respond to thermal stress before it becomes life-threatening.
Infants and very young children were the second-most-vulnerable population. Their high surface-area-to-volume ratio means they gain heat from the environment faster than adults, and their inability to communicate distress or access cooling independently makes them entirely dependent on caregivers who may themselves be heat-stressed.
Agricultural workers and others who performed outdoor physical labor during the heat wave were at extreme risk from the combination of exertion-generated heat, ambient extreme heat, and the dehydration that prolonged sweating without adequate fluid replacement produces. Farm workers in the Great Plains, already physically depleted by years of economic hardship and inadequate nutrition, faced heat conditions that would have challenged even well-nourished individuals in excellent health.
The absence of residential air conditioning made the 1936 heat wave categorically more dangerous than a comparable heat event today. Air conditioning existed in 1936 but was found almost exclusively in movie theaters, some commercial buildings, and a small number of wealthy residences. The overwhelming majority of the American public — including virtually everyone in the rural Great Plains and the small cities of the interior — had no access to mechanically cooled air of any kind. Home cooling consisted of whatever cross-ventilation open windows could provide on nights when outdoor temperatures allowed it — but in the 1936 heat wave, overnight lows frequently remained above 90°F, eliminating the nighttime recovery that allows the body to manage daytime heat stress.
The Cities That Suffocated
Heat mortality in urban areas during the 1936 heat wave was concentrated in tenement districts and working-class neighborhoods where housing density was highest, ventilation was poorest, and the urban heat island effect amplified already extreme temperatures. Cities across the Midwest recorded days when overnight temperatures in densely developed neighborhoods never dropped below 90°F — a condition that produced cumulative heat stress in residents who had no relief day or night.
Chicago, which would experience another catastrophic heat wave in 1995 that killed over 700 people and produced landmark research on urban heat mortality, lost hundreds of residents in the 1936 heat. St. Louis, Kansas City, and Cincinnati all recorded significant mortality during the summer’s worst weeks.
The pattern of who died in these cities — predominantly elderly people living alone in upper-floor apartments without cross-ventilation, without neighbors checking on them, without any mechanism for accessing cooling — would recur with tragic familiarity in subsequent heat waves across the following decades. The social isolation that amplifies heat mortality was as present in 1936 as in 1995 or in any heat wave since.
What 1936 Tells Us About Heat Today
The Heat Wave of 1936 is not simply a historical curiosity. It is the benchmark against which heat extremes are measured and the event that set the temperature records that current climate change projections suggest may eventually be challenged.
The persistence of 1936’s temperature records across the central United States is partly a function of the unique Dust Bowl conditions that amplified that summer’s heat beyond what the atmospheric pattern alone would have produced. The drought-stripped landscape that removed natural evaporative cooling was a one-time condition specific to the Dust Bowl era — the conservation programs described in the Black Sunday and dust storm pieces have significantly reduced the vulnerability of Plains landscapes to the same degree of soil exposure.
But the atmospheric pattern that produced 1936 — a persistent blocking high over the central United States during the summer — is not a one-time occurrence. Blocking patterns form regularly. What made 1936 exceptional was the combination of blocking pattern and drought-landscape feedback. If a comparable blocking pattern were to occur over a drought-stressed landscape — and the southwestern United States and portions of the central Plains have experienced significant drought in recent decades — the potential for extreme heat amplification exists.
The other variable that has changed dramatically since 1936 is the availability of air conditioning. The United States in 2025 is more than 90 percent air-conditioned in its residential housing stock, compared to near-zero in 1936. This single technological change has made comparable heat waves less deadly than they otherwise would be — though not safe, as the heat waves of 1980, 1995, and 2003 (which killed tens of thousands in Europe, where air conditioning penetration remained low) demonstrated.
Heat remains the deadliest weather hazard in the United States. It kills more people annually than tornadoes, hurricanes, and floods combined — a fact that the dramatic spectacle of those other hazards tends to obscure. The summer of 1936 established that reality in the most unambiguous terms possible, across a landscape that had already been pushed to its limits by years of drought and economic catastrophe.
As summer begins in 2025, the temperature records set in July 1936 still stand in state after state across the central United States. They are a benchmark nobody has been eager to challenge — and a reminder of what the atmosphere is capable of delivering when the right conditions align.
