Weather Toolbox - Weather Hazard Awareness - Temperature

This text is part of the Weather Preparedness & Resilience Toolbox developed by the YOUROPE Event Safety (YES) Group within YOUROPE’s 3F project (Future-Fit Festivals). It is aimed at everyone involved in planning, building, and operating open-air events. It helps festivals and other outdoor events become truly weather-ready by offering both practical and research-based resources as well as background information on weather and climate. Learn how to design safer and more weather-resilient outdoor events.

Weather Toolbox – Weather Hazard Awareness – Temperature

Weather Hazard Awareness: What are we dealing with?

Temperature related Phenomena

Weather hazard awareness for temperature-related phenomena starts with understanding how heat and cold episodes form, how they impact people and infrastructure, and why they are changing in Europe. For crowd and event managers, these processes translate directly into health risks, reduced working capacity, surface and ground hazards, and growing regulatory expectations.

1 Heat and high temperature episodes

Heat episodes typically develop under a stable high‑pressure system, where air slowly sinks, warms, and suppresses cloud formation. This allows intense solar radiation to reach the ground throughout the day, while light winds prevent mixing and keep the heat trapped near the surface. In urban and event environments, dark pavements, stages, vehicles, generators, and dense crowds further increase near‑surface temperatures and thermal load. Persistent daily heat without sufficient night‑time relief raises physiological strain and sharply increases the risk of dehydration, heat exhaustion, and reduced outdoor working capacity for staff and visitors.

For Europe, these hot spells are no longer rare “exceptions” but a recurrent hazard. Observations over the last decades show that European heat extremes are increasing in frequency, intensity, and duration, with heatwave indicators rising around three to four times faster than in other northern mid‑latitudes. This trend is driven by overall warming and by circulation changes, including more persistent high‑pressure “blocking” patterns and altered jet‑stream configurations that lock hot, dry air over the continent for longer periods.

2 Heatwaves

Heatwaves are extended periods of unusually high temperatures, often lasting several days to weeks and including hot nights with limited cooling.

In recent years, Europe has emerged as a global heatwave “hotspot”, with a marked increase in both the number of heatwave days and their cumulative intensity. This has direct implications for crowd safety: more frequent and more intense heatwaves increase the likelihood that outdoor events coincide with dangerous thermal stress, power system strain, and wildfire risk, demanding robust heat action plans, shading strategies, water provision, medical readiness, and flexible work‑rest schedules.

3 Cold spells and low temperature periods

Cold spells are multi‑day periods of unusually low temperatures caused by the southward displacement of polar or Arctic air masses. Even in a warming climate, severe cold‑air outbreaks over Europe have remained nearly as intense and as frequent as in previous decades, because circulation patterns can still favour strong incursions of cold air.

During clear, calm nights within a cold spell, heat rapidly radiates from the ground into the atmosphere and space, allowing near‑surface temperatures to drop sharply. For events and venues, this can lead to hard, frozen ground, slippery surfaces, cold stress for staff and visitors, and increased vulnerability of technical systems, water lines, and temporary structures to freezing. Crowd managers must account for wind‑chill, prolonged exposure, and reduced fine motor performance when planning staffing, PPE, and emergency response in low‑temperature scenarios.

4 Frost and near‑surface hazards

Frost occurs when surfaces cool to 0 °C or below, allowing ice crystals to form, even if the official air temperature at standard measurement height remains slightly above freezing. The key drivers are strong radiative cooling under clear skies, low humidity, and light or calm winds that prevent warmer air from mixing down to the surface. Cold air tends to pool in low‑lying areas and depressions, so frost can form very locally on grass, roofs, stages, cables, steps, or roads while nearby elevated instruments still report positive temperatures.

From an operational perspective, frost is less about headline “extreme” weather and more about subtle but critical surface hazards. Light radiative frosts can produce black ice on walkways, ladders, ramps, and platforms, damage sensitive equipment, and affect vehicle manoeuvrability and evacuation routes. Because frost often develops late at night or in the early morning hours, before inspections or gates open, systematic pre‑event checks, anti‑slip treatments, and targeted de‑icing protocols are essential elements of a weather safety toolbox.

Temperature hazards at events: key aspects

For crowd and event safety management, temperature‑related hazards combine atmospheric processes with human and infrastructural vulnerabilities. Key dimensions include:

Human health: Heatwaves drive excess mortality, dehydration, cardiovascular stress, and reduced cognitive and physical performance, while cold spells increase hypothermia, frostbite risk, and cardiovascular incidents, especially in vulnerable groups.
Infrastructure and operations: High temperatures strain power supplies, cooling systems, and water demand, while low temperatures and frost affect structural materials, anchoring, ground stability, and technical reliability.
Surface and crowd movement: Hot, radiating surfaces contribute to heat load and burns, whereas frost and frozen ground create slip, trip, and fall hazards that can cascade rapidly in dense crowds.
Changing risk baseline: Climate change is intensifying European heatwaves and altering circulation patterns, while still allowing severe cold spells; this widening range of extremes requires proactive, scenario‑based planning rather than reliance on historical experience alone.

More information

Weather Toolbox – Weather Hazard Awareness – Temperature

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