Heat and temperature predictions 2026: heat waves, record heat, and what causes them

Temperature prediction markets allow traders to forecast two distinct weather metrics: local daily temperature outcomes and broader climate anomalies.

The first type of market settles on the official daily high recorded at a city's designated observation station (such as an airport weather station or official municipal sensor). The second type settles on global temperature anomalies, which track the difference between an entire month or year's average temperature and a fixed historical baseline, published by NASA's Goddard Institute for Space Studies (GISS) and NOAA.

What is a heat wave?

A heat wave is a stretch of abnormally hot weather lasting at least two days, though no single official definition exists across meteorological agencies. The National Weather Service defines a heat wave as a period of abnormally and uncomfortably hot, unusually humid weather typically lasting two or more days.

Stricter research definitions require five consecutive days where daily maximum temperatures exceed the local 1961 to 1990 average by at least 5 degrees Celsius.

What is the hottest temperature ever recorded?

The hottest temperature ever directly recorded is 56.7 degrees Celsius (134 degrees Fahrenheit), measured at Furnace Creek in Death Valley, California, on July 10, 1913. This reading remains the official record in the World Meteorological Organization Weather and Climate Extremes archive.

This historical figure remains subject to academic debate. Modern meteorological reviews suggest the 1913 reading may have involved an inexperienced observer using non-standard equipment housing, estimating that the true maximum was closer to 51.7 degrees Celsius. Overturning the official record requires a formal investigation by the World Meteorological Organization, which has not been convened, leaving the 1913 reading as the standing official mark.

Hottest year records use a completely different methodology. Rather than relying on a single station's extreme, annual records rank full calendar years by global average anomaly. NASA GISS ranks 2024 as the warmest year in its 146-year record at 1.28 degrees Celsius above the 1951 to 1980 baseline, with 2025 and 2023 effectively tied for second within the agency's margin of error (NASA GISS, January 2026).

What causes heat waves?

Heat waves are caused by stagnant high-pressure systems that park over a region and prevent warm air from rising. As air under the high pressure is forced downward, it compresses and warms. This suppression prevents cloud formation, allowing uninterrupted sunlight to heat the dry ground for consecutive days and driving morning temperatures higher each day.

Atmospheric stalling is the key factor in severe heat events. While the jet stream typically moves weather systems across continents, a jet stream that buckles into large, slow-moving waves can lock a high-pressure system in place, a situation forecasters refer to as a blocking pattern. A high-pressure system trapped this way forms a heat dome, defined by the American Meteorological Society as an exceptionally warm air mass under upper-level high pressure.

Slower climate cycles operate underneath these immediate weather patterns. El Nino, the warm phase of the El Nino-Southern Oscillation (ENSO) in the central Pacific, raises global average temperatures over extended months. A blocking high dictates a single day's station reading, while an ENSO phase influences where an entire year ranks globally.

Hottest and coldest years on record.

• 2024: The hottest year on record, measuring 1.28°C above the 1951 to 1980 baseline.
• 2025: Second warmest year, measuring 1.19°C above baseline, effectively tied with 2023 within NASA's margin of error.
• 2023: Third warmest year, measuring 1.17°C above baseline, driven by a rapidly developing El Nino that peaked in December.
• 2016: Tied for fourth warmest at 1.01°C above baseline, following one of the strongest recorded El Nino events.
• 2020: Tied for fourth warmest at 1.01°C above baseline, achieved despite La Nina conditions in the Pacific.
• 2019: Sixth warmest year on record at 0.98°C above baseline.
• 2017: Seventh warmest year at 0.91°C above baseline, marking the warmest year up to that point without an El Nino boost.
• 1983: Location of the coldest temperature ever recorded, measuring minus 89.2°C at Vostok Station, Antarctica, on July 21.