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Understanding the 12 types of heat waves as Maricopa County sizzles under extreme temperatures

According to the NOAA Climate Prediction Center in July, a total of 594 counties are expected to have five or more extremely hot days.

BY STAFF WRITER

UPDATED JUL 5, 2024

Heat-related deaths have been increasing in the US.

Phoenix, Arizona: According to the NOAA Climate Prediction Center in July, a total of 594 counties across Texas (126), Montana (41), Kansas (38), Oklahoma (37), Georgia (32), Idaho (30), California (26), Colorado (26), Utah (23), South Dakota (22), South Carolina (16), Arizona (15), Nebraska (15), New Mexico (15), Nevada (15), Virginia (14), Wyoming (13), Pennsylvania (12), Alabama (11), Arkansas (11), North Carolina (11), Washington (8), Missouri (7), Oregon (7), West Virginia (7), North Dakota (4), Maryland (3), Kentucky (2), Louisiana (2), Florida (1), Iowa (1), Mississippi (1), Tennessee (1), and Vermont (1) are expected to have five or more extremely hot days.

In these counties, the total population at risk is 62,859,224.Extreme summer heat is already increasing in the US and climate projections indicate that extreme heat events will become more frequent and intense in coming decades. Heat-related deaths have been increasing in the US, with approximately 1,602 occurring in 2021, 1,722 in 2022, and 2,302 in 2023.

Extreme summer heat is already increasing in the US. (Source: US Department of Human Health and Services)

Understanding heat waves

There are 12 different types of heat waves based on their intensity, duration, geographical impact, and the underlying meteorological conditions.

Meteorological

Classical Heat Waves: Prolonged periods of excessively hot weather, which may be accompanied by high humidity. They are typically defined by a significant and sustained departure from the normal temperature range.

Blocking Heat Waves: These occur when a high-pressure system remains stationary over a region, blocking the movement of weather systems and leading to prolonged hot and dry conditions.

Geographical

Continental Heat Waves: These affect large continental areas and can cover extensive regions, often impacting multiple countries.

Regional or Local Heat Waves: These are confined to smaller areas, such as specific states, provinces, or metropolitan regions.

Intensity-Based

Moderate Heat Waves: Characterized by temperatures that are significantly above average but not extreme. They can pose risks especially to vulnerable populations.

Severe Heat Waves: Marked by extremely high temperatures that can pose serious health risks and cause widespread disruption. They often result in increased mortality rates and strain on infrastructure.

Extreme Heat Waves: Represent the most intense category, with record-breaking temperatures that can lead to catastrophic impacts on health, agriculture, and infrastructure.

Duration-Based

Short-Duration Heat Waves: Lasting for a few days, these heat waves can cause acute health effects but are generally less impactful than longer events.

Prolonged Heat Waves: Extending over weeks, these can have severe and cumulative effects on public health, agriculture, and ecosystems.

Health-Based

Health Alert Heat Waves: Identified based on the potential for causing significant health impacts. These are often declared by public health agencies based on temperature thresholds and humidity levels.

Agricultural and Environmental

Agricultural Heat Waves: Defined based on their impact on crop production and livestock. These heat waves can lead to drought conditions and affect food supply.

Ecological Heat Waves: Affect natural ecosystems, causing stress to wildlife and plant communities. They can result in forest fires, loss of biodiversity, and habitat degradation.