Heat, Wildfire Smoke & T2D: What Every BC Provider Needs to Know This Summer
- t2diabetesnetwork
- 7 hours ago
- 6 min read
Written by Clare Koning, RN, PhD 6 min read
Key Highlights:
✅ Diabetes was independently associated with increased odds of death during BC's 2021 heat dome.
✅ People with T2D have impaired thermoregulation, they cannot cool themselves as effectively as people without diabetes.
✅ Wildfire smoke PM2.5 drives systemic inflammation and insulin resistance, worsening glycemic control.
✅ Insulin degrades above 30°C, often without any visible change in appearance.
✅ BC has a Heat Alert and Response System (BC HARS), providers should know how it works and what it triggers.
British Columbia's summers have changed. What was once a season of reliable mild weather is now defined by heat events that break records, wildfire seasons that extend from June through October, and smoke advisories that keep patients indoors for weeks at a time. For people living with type 2 diabetes, these are not inconveniences, they are clinical risks.
The 2021 western heat dome killed 619 British Columbians in six days, the deadliest weather event in Canadian history. A peer-reviewed analysis published in GeoHealth found that diabetes was independently associated with increased odds of death during that event, alongside depression and chronic kidney disease. More than 80% of those who died were on three or more chronic disease registries.
This is not a distant public health statistic. It is a clinical reality that providers across BC will face again, likely this summer.
Why People with T2D Are at Higher Risk in the Heat
Most people understand that extreme heat is dangerous. What is less widely appreciated is that diabetes specifically impairs the body's ability to respond to heat stress, through mechanisms that are well-established in the physiological literature.
Impaired thermoregulation.
The primary way the body cools itself is through sweating and skin vasodilation. Both of these mechanisms are compromised in people with diabetes. Autonomic neuropathy, a common complication of longstanding T2D, reduces sweat gland function, limiting the body's capacity to dissipate heat through evaporative cooling.
A comprehensive review (while written some time ago, is still relevant today) in Temperature describes how both sweating capacity and skin blood flow responses to heat are significantly blunted in people with T2D compared to matched controls, and that these impairments worsen with longer duration of diabetes and poorer glycemic control.
People with T2D can overheat before they feel hot.
Dehydration and glucose fluctuation.
Heat causes fluid loss through sweating, reduced as it may be, and through increased insensible losses. Dehydration concentrates blood glucose, raising HbA1c-independent acute hyperglycemia risk. Conversely, some patients on sulphonylureas or insulin who are eating less in the heat, exercising more, or who have reduced appetite during extreme heat events face compounded hypoglycemia risk. A 2025 systematic review in Frontiers in Public Health confirmed that extreme heat events are associated with increased diabetes-related hospitalizations and mortality globally.
Cardiovascular vulnerability.
T2D is already a major cardiovascular risk factor. Extreme heat places additional stress on the cardiovascular system through increased heart rate, vasodilation, and fluid shifts, a compounding burden for patients already managing hypertension, heart failure, or CKD alongside their diabetes.
Hypoglycemia masking.
Heat stress and its symptoms, dizziness, weakness, sweating, confusion, overlap substantially with hypoglycemia symptoms. In patients with impaired hypoglycemia awareness (itself more common in longstanding T2D), this masking can delay recognition and response to a low blood glucose event.
The Insulin Storage Problem No One Is Talking About
One of the most practically urgent, and most commonly overlooked, clinical issues in summer diabetes care is insulin degradation.
Insulin is a protein. It is irreversibly damaged by heat. Manufacturers recommend that unopened insulin be stored refrigerated at 2–8°C, and that insulin in use not exceed 30°C for more than 28 days. A 2023 Cochrane systematic review on insulin storage confirmed the temperature sensitivity of human insulin and noted that degradation can occur without any visible change in the insulin's appearance – no cloudiness, no particles, no obvious sign that the medication has lost potency.
This matters enormously for patients during heat events. A car parked in the sun can reach 60°C within 20 minutes. A home without air conditioning during a multi-day heat event can sustain indoor temperatures above 35°C for extended periods, exactly the conditions that killed the majority of BC's 2021 heat dome victims, most of whom died inside their own homes.
Patients may be injecting degraded insulin, experiencing unexpected hyperglycemia, and not connecting these events to the heat. The medication looks fine. The dose is correct. The blood sugar makes no sense.
What to advise patients:
Never leave insulin in a parked car, direct sunlight, or near a window in summer
Use an insulated medication case or cooling wallet during hot weather (not an ice pack directly on insulin – freezing also destroys it)
If insulin has been exposed to sustained heat above 30°C, treat it as potentially compromised and contact their pharmacy or provider
GLP-1 receptor agonists (semaglutide, tirzepatide, liraglutide) are similarly temperature-sensitive – the same guidance applies
Wildfire Smoke: A Distinct and Underappreciated Risk for People with T2D
Extreme heat and wildfire smoke increasingly co-occur in BC, and their effects on people with T2D compound each other in ways that the clinical literature is only beginning to quantify.
Wildfire smoke is dominated by fine particulate matter (PM2.5) at concentrations that can far exceed urban pollution levels even hundreds of kilometres from a fire. When inhaled, PM2.5 penetrates deep into the alveoli, enters the bloodstream, and triggers systemic inflammation, oxidative stress, endothelial dysfunction, and platelet activation, the same biological pathways that drive cardiovascular disease and worsen insulin resistance.
A landmark 2024 study published in Diabetes Care, the first large multi-country analysis of its kind, found that short-term exposure to wildfire-specific PM2.5 was associated with a statistically significant increase in diabetes hospitalizations. A concurrent analysis published in PNAS confirmed that long-term wildfire smoke PM2.5 exposure is associated with endocrine disease and diabetes mortality in a dose-dependent relationship across the contiguous United States.
The mechanism is clinically coherent: PM2.5 exposure drives insulin resistance through inflammatory cytokine release and impairs microvascular function, exactly the pathophysiology that people with T2D are already managing. For patients with pre-existing endothelial dysfunction, the effect of wildfire smoke exposure is amplified, as confirmed in a 2023 review in Frontiers in Cardiovascular Medicine.
For BC providers, this means that a patient presenting with unexplained glycemic deterioration during wildfire season, without changes to diet, medication, or activity, may be experiencing a smoke-driven inflammatory response. This is not yet widely recognized in primary care, and the evidence base is growing faster than clinical awareness.
What to advise patients during smoke events:
Stay indoors with windows closed when the Air Quality Health Index (AQHI) is high, check weather.gc.ca for real-time BC air quality data
Use N95 or KN95 masks if outdoor exposure is unavoidable, standard surgical masks do not filter PM2.5 effectively
Increase blood glucose monitoring frequency during prolonged smoke events
Advise patients that worsening glycemic control during wildfire season may not be a self-management failure
The BC Heat Alert and Response System: What Providers Should Know
Following the 2021 heat dome, BC launched the BC Heat Alert and Response System (BC HARS), coordinated by the BCCDC, the Ministry of Health, and Health Emergency Management BC. It operates on two tiers:
Heat Warning: issued by Environment and Climate Change Canada (ECCC) when regional temperature thresholds are met; triggers public health actions including activation of cooling centres
Extreme Heat Emergency: triggers a Broadcast Intrusive Alert through the Alert Ready system province-wide; activates emergency operations coordination
When a Heat Warning or Extreme Heat Emergency is declared, BC HARS activates a series of recommended provider actions, including proactive outreach to high-risk patients. People with diabetes are explicitly named as a high-risk group.
Practical steps for providers and practices:
Identify high-risk patients on your panel now, before summer heat events begin. Patients on insulin, sulphonylureas, diuretics, or ACE inhibitors face compounded risk
Ensure your diabetic patients know how to access cooling centres during heat events. BC's interactive cooling centre map is updated in real time during heat events
Review medication lists with heat in mind: diuretics in a heat event can accelerate dehydration; SGLT2 inhibitors increase fluid losses and may compound dehydration risk if patients are not adequately hydrated
Brief patients on insulin storage before summer, not during a crisis
Know how to refer patients to HealthLink BC (8-1-1) for non-emergency heat-related guidance
A Note on Equity
The risks of extreme heat and wildfire smoke are not distributed equally. BC's 2021 heat dome analysis confirmed that deaths were concentrated in deprived neighbourhoods without air conditioning or green space. Many of BC's most heat-vulnerable patients, older adults, people in social housing, individuals experiencing housing insecurity, and people in remote and northern communities, are the same populations most likely to have uncontrolled T2D and limited access to emergency resources.
Indigenous communities in BC face compounded vulnerability: higher rates of T2D, more frequent exposure to wildfire smoke from fires on or near their traditional territories, and health infrastructure that is often less resilient to climate emergencies. Providers working with these communities should engage with the First Nations Health Authority's climate and environmental health resources and ensure patients have access to FNHA-supported programs and services.
Climate change is not a future health issue. For your patients with T2D in British Columbia, it is happening now, this summer, likely this month. The clinical tools to respond are available. The evidence is clear. What's needed is integration of climate awareness into everyday diabetes care.
The T2D Network is committed to supporting evidence-informed, equitable diabetes care across British Columbia. Content reviewed for clinical accuracy. For more resources, visit t2dnetwork.ca.
