Although Minnesotans live in a cold weather state, the summer heat can significantly impact our health. Heat events - prolonged periods of hot weather - cause more deaths than any other natural disaster. Hot weather can increase your core body temperature, making it difficult for your body to function normally. This can be demanding on your body and lead to heat-related illnesses and even death. Heat-related illness includes: dehydration, heat stress, heat exhaustion, and heat stroke, that occur when the body becomes too hot and cannot cool down adequately. Heat also can worsen existing chronic conditions such as: diabetes, heart disease, and respiratory conditions.
Learn more about heat, and what is being done about it in Minnesota
The Minnesota Department of Health (MDH) Climate and Health Program has created a suite of tools to aid local governments and public health professionals prepare for, and respond to, extreme heat events. Extreme Heat Events-MDH
In addition, the Centers for Disease Control and Prevention developed resources for emergency preparedness and response for Extreme Heat-CDC.
Heat can cause acute illness that can sometimes require an emergency department visit (ED visit). ED visit data includes patients that were treated in the ED and then either released or hospitalized for further care. ED visit data include more patients than hospitalization data because most people visit the ED first. ED visits due to heat are sometimes not coded as heat-related, which can mean that the data underestimate heat-related ED visits.
Emergency department visits by year
Emergency department visit rate by year
Emergency department visit rate by region
Emergency department visit rate by month
Emergency department visit rate by age
Emergency department visit rate by age and sex
Number of heat-related illness emergency department visits by year
Summertime heat-related emergency department (ED) visits vary widely from year to year.
Source: Minnesota Hospital Association
Heat-related illness emergency department visits by year
Rates of summertime heat-related emergency department (ED) visits vary widely from year to year.
Source: Minnesota Hospital Association. The break indicates a change in International Classification of Disease (ICD) coding from ICD-9 to ICD-10 on October 1st, 2015. Rates from 2000-2014 should not be compared to rates from 2015 onward.
Heat-related illness emergency department visits by Minnesota regions
Urban populations are generally considered at higher risk for heat-related illness due to the urban heat island effect. General trends show that non-metro populations in Minnesota consistently experience higher rates of heat-related emergency department (ED) visits compared to the metro population, until this most recent year. Some populations are more vulnerable to heat-related illness than others. Data on the percentage of vulnerable populations by census tracts throughout Minnesota are available under population vulnerability maps
Source: Minnesota Hospital Association. The break indicates a change in International Classification of Disease (ICD) coding from ICD-9 to ICD-10 on October 1st, 2015. Rates from 2000-2014 should not be compared to rates from 2015 onward.
Monthly heat-related illness emergency department visits, 2000-2022
There are more heat-related illness emergency department (ED) visits in July, corresponding with higher summer temperatures.
Source: Minnesota Hospital Association
Heat-related illness emergency department visits by age
This chart shows ED visits by age group. Though the number and rate change year to year, trends show that 15-34 year olds and adults over 65 consistently have higher rates of heat-related emergency department (ED) visits than other age groups.
Source: Minnesota Hospital Association. The break indicates a change in International Classification of Disease (ICD) coding from ICD-9 to ICD-10 on October 1st, 2015. Rates from 2000-2014 should not be compared to rates from 2015 onward.
Heat-related illness emergency department visits by sex and age, 2018-2022
While people 65 years old and older are considered the most sensitive to heat, this chart indicates that males age 15 to 34 have the highest rate of heat-related illness emergency department (ED) visits. This differs from the hospitalization data where males age 65 years old and older had the highest rate of hospitalization.
Source: Minnesota Hospital Association
Emergency department visit rates (County)
Emergency department visit rates compared to MN average (County)
Heat-related illness emergency department visits by county, 2018-2022
The map of heat-related illness map shows higher rates in south central Minnesota. The overall Minnesota rate is 13 visits per 100,000 people.
Source: Minnesota Hospital Association. Rates based on counts less than or equal to 20 should be interpreted with caution; the rate maybe unstable because it can change dramatically with the addition or subtraction of one case. To protect an individual's privacy, hospitalization counts under 5 are suppressed if the underlying population is less than or equal to 100,000.
Heat-related illness emergency department visits by county compared to Minnesota overall, 2018-2022
This map shows which counties have higher, the same, and lower rates as compared to the overall state rate.The overall Minnesota rate is 13 visits per 100,000 people.
Heat-related illness encompasses many health problems such as: dehydration, heat stress, heat exhaustion, and heat stroke, that occur when the body becomes too hot and cannot cool down adequately.
Heat index is a combined measure of air temperature and relative humidity that indicates how hot it really feels. Many health agencies throughout the United States, with assistance from the National Weather Service, use heat index to communicate health risk due to hot weather.
Data Sources
Hospitalization and ED data are extracted from Minnesota Hospital Discharge Data (MNHDD), which is maintained by the Minnesota Hospital Association (MHA).
MHA data are periodically revised by the MHA to reflect more complete and accurate discharge information.
Mortality/Death data are extracted from the Minnesota Mortality Database, which is maintained by the MN Center for Health Statistics at the Minnesota Department of Health.
The numbers and rates of hospitalizations, emergency department (ED) visits, or deaths directly attributed to heat-related illness by year, gender, or age group in Minnesota.
If a segment of a population is at higher risk for hospitalization, a visit to the ED, or death resulting from heat in Minnesota.
Allow for a better understanding of spatial and temporal trends of extreme heat.
Average heat index by county in Minnesota.
Number of days of extreme heat in each county in Minnesota.
How heat index relates to heat-illness by year and month.
Provide information to the public about heat-related illness hospitalizations, ED visits, and deaths in Minnesota.
State and local partners can use these data for program planning and evaluation.
The general public can use this information to better understand temperature distribution in Minnesota and their area’s risk of extreme heat.
These hot weather data and maps can be used to:
Inform which Minnesota counties should be targeted for outreach and prevention efforts.
Educate the public about the health effects from extreme temperature.
The total burden of heat-related illness in a population.
The number of people hospitalized or who visited the ED for heat-related illness. Because personal identifiers are removed from the hospital discharge data before analysis, we cannot identify individuals who may receive care at more than one facility.
Heat-related illness can manifest in numerous and unobvious ways, for this reason heat may not be listed as the primary diagnosis. This analysis only captures cases where heat-related illness is explicitly listed and thus does not capture the full extent of heat-related illness, since they are sometimes not coded as heat-related.
Deaths attributed to heat are very rare because often heat-related illness may not be listed as the underlying cause of death. This analysis only includes deaths where heat-related illness is explicitly recorded as an underlying or contributing cause of death and does not capture the full extent of heat-related deaths.
Hospitalizations/ED visits:
Minnesota residents who are hospitalized or visit the emergency department in the warm weather months (May-September) with a diagnosis of directly attributable heat-related illness, defined as having any of the following ICD-9-CM codes: 992.0-992.9, E900.0, and E900.9 and ICD-10-CM codes: T67, X30, or X32 (excluding cases with a code W92).
The data source for hospitalizations and ED visits is the Minnesota Hospital Discharge Data. The Minnesota Hospital Discharge Data collects hospital discharge information from acute care hospitals submitting data to the Minnesota Hospital Association (MHA). MN EPHT receives Minnesota Hospital Discharge Data from the Injury and Violence Prevention Unit at MDH.
Hospitalizations include out-of-state hospitalizations of Minnesota residents in the nearby states of North Dakota, South Dakota, and Iowa. ED visits only include out -of-state hospitalizations of Minnesota residents after the year 2005.
Deaths:
Minnesota residents deceased during the warm weather months (May-September) with ICD-10 code T67(heat-related illness) listed as a contributing cause of death on the death certificate record or accompanied by ICD-10 code X30 as a contributing cause of death.
The data source for deaths is the Minnesota Mortality Data, which contains information on demographic and cause of death data collected from death certificates. Minnesota Mortality Data is maintained by the Center for Health Statistics at MDH. MN EPHT receives Minnesota Mortality data from the Injury and Violence Prevention Unit at MDH.
Code
Description
X30
Exposure to excessive natural heat
T67.0
Heat stroke and sunstroke
T67.1
Heat syncope (fainting)
T67.2
Heat cramps
T67.3
Heat exhaustion w/ water depletion
T67.4
Heat exhaustion from salt depletion
T67.5
Heat exhaustion, unspecified
T67.6
Heat fatigue, transient
T67.7
Heat edema (swelling)
T67.8
Other unspecified heat effects
T67.9
Unspecified effects of heat and light
The average summer heat index from 2019-2022 was determined by averaging the maximum daily heat index from May through September for the three years for each county. Three years of data were used to determine the average heat index because temperatures can vary considerably every year. Looking at multiple years helps to provide a better understanding of typical temperatures.
For this analysis, extreme heat days were defined as days that had a heat index over the 95th percentile of the baseline (based on the daily heat index for the years 1991-2020).
Only Minnesota resident data from Minnesota death certificate records are included in the analysis; this excludes out-of-state deaths. Before 2005, ED visits did not include out-of-state ED visits for Minnesota residents. Hospitalization and ED visit rates for counties in which residents are likely to cross state lines for care may be underestimated. Rates for counties whose residents are likely to visit hospitals that do not submit data to the Minnesota Hospital Association (e.g., Veteran's Administration or Indian Health Services hospitals) may also be artificially low.
Multiple hospital or emergency department admissions by the same patient cannot be identified, and are not excluded.
Heat-related illness can exacerbate a number of chronic diseases and conditions, yet in a heat wave many of these conditions often are not attributed to heat exposure. This data only captures heat health outcomes that have been coded as attributed to heat.
Since only people with the most severe or acute symptoms of heat-related illness are hospitalized, treated at the ED, or die, these data are not appropriate for estimating the total burden of heat-related illness in a population. The actual number of Minnesotans who experience heat-related illness is unknown. Heat-related illness is not currently a reportable condition in Minnesota.
Mortality rates were not calculated due to the low number of deaths attributed to heat in Minnesota.
Modeled data performs relatively well in estimating temperature, however, the estimates may differ when compared to weather station-based observations. The differences vary by region and some of these differences are expected from a meteorological perspective. As a result, an area may be described as having higher or lower temperatures than actually occurred.
County-level estimates of temperature and heat index are obtained by processing modeled data, which are available by 1/8th-degree grid. The process of converting grid-level data to county-level estimates using a population-weighted approach may lead to potential misclassification of temperature and heat index for some areas.
Values for heat index are not calculated for days with a maximum daily temperature less than 80 degrees Fahrenheit resulting in some missing values.
To learn more about heat-related illness and hot weather, visit Extreme Heat Events.
For more information about the heat-related illness data and measures, contact MN Tracking.
