Exceptional heat and rain, wildfires and floods mark summer of extremes

China set a new national daily temperature record in July, and was hit by record-breaking rainfall at the start of August. Many new station temperature records around the world were broken in July. The start of August also saw a winter heatwave in parts of South America.

Wildfires caused devastation and dozens of casualties and forced evacuations of thousands of people in Canada, parts of the Mediterranean, including Algeria, Greece, Italy and Spain.

Canada has seen its worst wildfire season on record, harming air quality for millions of people in North America. Fires are now burning in the Canadian Arctic. The Copernicus Atmosphere Monitoring Service (CAMS) reported that as of the end of July, the total estimated wildfire carbon emissions for the year to date reached double the previous Canadian annual total. CAMS recorded a significant increase in intensity and emissions from wildfires in the eastern Mediterranean during the second half of July, particularly in Greece. In accordance with the GFAS dataset, the emissions from these wildfires have been the highest for this period of time in Greece in the last 21 years. 

Sea surface temperatures have hit new records, with severe marine heatwaves in the Mediterranean and off the coast of Florida. The US National Oceanic and Atmospheric Administration said that the ongoing heat stress in Florida has not been this high this early in the season since satellite records began in 1985.

“The extreme weather – an increasingly frequent occurrence in our warming climate – is having a major impact on human health, ecosystems, economies, agriculture, energy and water supplies. This underlines the increasing urgency of cutting greenhouse gas emissions as quickly and as deeply as possible,” said WMO Secretary-General Prof. Petteri Taalas.

“In addition, we have to step up efforts to help society adapt to what is unfortunately becoming the new normal. The WMO community is providing forecasts and warnings to protect lives and livelihoods as we strive to achieve our goal of Early Warnings for All,” said Prof. Taalas.

A rapid study from climate scientists in the World Weather Attribution network said that the heatwaves bore the clear footprint of climate change.

“ Without human induced climate change these heat events would however have been extremely rare. In China it would have been about a 1 in 250 year event while maximum heat like in July 2023 would have been virtually impossible to occur in the US/Mexico region and Southern Europe if humans had not warmed the planet by burning fossil fuels,” said the attribution study published on 25 July.

The developing El Niño is expected to further fuel land and ocean temperatures.

Heatwaves

Heatwaves are amongst the deadliest natural hazards with thousands of people dying from heat-related causes each year. The full impact of a heatwave is often not known until weeks or months afterwards, WMO experts told a media briefing on 18 July.

France, Greece, Italy, Spain, Algeria and Tunisia reported new maximum daytime and overnight station temperature records.

For instance, Figueres (Catalonia), reported a new temperature record of 45.4 °C on 18 July (provisional all-time maximum). A station on the Italian island of Sardinia recorded 48.2°C on 24 July.

In Algeria and Tunisia, the highest maximum temperature was respectively 48.7 °C (Dar El Beïda/Argel) and 49.0 °C (Tunis and Kairouan) on 23 July.

Temperatures in Iran topped 50°C in early August.

"An increasing number of studies demonstrate connections between rapid warming and the Arctic and mid-latitude weather patterns, including in atmsopheric dynamics such as the jet stream. The jet stream becomes weaker and wavier when warm air is transported to the north and cold air to the south. In these conditions, near-stationary weather patterns establish and lead to prolonged heatwaves and drought in some regions and heavy precipitation in others," said Alvaro Silva, an expert with WMO climate services division.

Sanbao weather station in Turpan city in China's Xinjiang province, had a temperature of 52.2°C on 16 July, setting a new national temperature record according to a report by the China Meteorological Administration.

North America

Large parts of the USA also were gripped by extensive heatwaves, with high temperatures in numerous places, according to the US National Weather Service. It issued repeated excessive heat warnings and advisories, often covering more than 100 million people. In the latest update issued on 31 July, it warned that the dangerous heat in the affected areas would continue through 5 August.

July was the hottest month on record for Phoenix, Arizona, with an average temperature of 102.7°F (39.3°C), according to the US National Weather Service.

Phoenix, Arizona, recorded 31 days, as of 30 July, of daytime temperatures above 110 °F (43.3 °C). Overnight low temperatures were repeatedly more than 90°F (32.2°C), according to the National Weather Service. 

"We need to broaden focus beyond maximum temperatures because the minimum temperature is most important for health and critical infastructure," said WMO extreme heat senior advisor John Nairn.

July was also the warmest month on record for Miami in Florida, with a mean average temperature of 86.5°F (30.3° C).

A temperature sensor at Furnace Creek in Death Valley National Park in California recorded 128 °C (53.3°C) on 16 July.  

According to the WMO Archive of Weather and Climate Extremes, the hottest temperature ever recorded was in Furnace Creek, Death Valley, California at 56.7°C on 10 July 1913.

South America

August opened with unusual heat in parts of South America – including parts of Argentina, Brazil, Chile and Uruguay.

Chile recorded its second highest winter temperature in history for a winter day with 37.0°C in the city of Vicuña. Northern and Central Argentina saw temperatures up to 38° C, according to the Argentina’s national meteorological and hydrological service, SMN.

Wildfires

Wildfires forced the evacuation of hundreds of residents and tourists on the Greek islands of Rhodes, Evia and Corfu since 17 July. The emissions of these wildfires have reached record levels, with an estimated total of 1 megaton of carbon emissions between 1 July and 25 July, almost doubling the July 2007 record, following several days of high intensity fires, according to Copernicus Atmospheric Monitoring Service.

In Algeria, there were several dozen reported casualties.

Hot, dry conditions have fueled an early an intense wildfire season in Canada (since the spring). The fires have forced more than 120 000 people to evacuate their homes and polluted the air for millions of people across North America.

In Canada, record-breaking wildfires continue to burn big forest areas. More than 650 wildfires were out of control as of 24 July. According to the Canadian Interagency Forest Fire Centre more than 11 million hectares already burnt in 2023 – compared to the 10-year average of about 800,000 hectares.

The record levels of emissions generated by the intense wildfire activity across Canada in May and June had a major impact on air quality, both in Canada and further afield. According to CAMS data, fire radiative power (FRP) for the country as a whole in the first three weeks of June was significantly higher than the 2003-2022 mean, with estimated carbon emissions at over 100 megatonnes for the month. Emissions levels from the start of the year until the first week of May remained close to the 2003-2022 mean, but then quickly rose to significantly higher than any previous year in the CAMS record (see right-hand graph below).

The fires continued to rage at the end of July, with numerous fires breaking out within Canada's Arctic circle.

Marine Heatwaves

Sea surface temperatures (SSTs) of the Mediterranean Sea are exceptionally high over the coming days and weeks, exceeding 30 °C in some parts, and more than 4 °C above average in a large part of the western Mediterranean.

Unconfirmed reports said that Manatee Bay, Florida, recorded a sea surface temperature of 101.1°F (38.4°C) – warmer than a hot bath.

The impacts of marine heatwaves impacts include migration of species and extinctions, arrival of invasive species with consequences for fisheries and aquaculture.

Heavy rains and floods

Heavy rains and flooding caused severe damage and loss of life in several parts of the world, especially Asia.

Record-breaking rainfall induced by tropical cyclones has caused devastation and casualties in the Chinese capital Beijing and the surrounding province of Hebei, prompting a major relief and rescue operation.

Beijing recorded its heaviest rainfall over the past few days since records began 140 years ago. It logged 744.8 millimeters of rain, the maximum amount of precipitation recorded during the rainstorm, between 8 p.m. on Saturday 29 July and 7 a.m. Wednesday 2 August at a city reservoir,  according to the Beijing Meteorological Service in a report cited by the Xinhua News Agency. Floods in Northwest China killed a reported 15 people in July.

Forty people were reported killed as torrential rain and flash floods hit the Republic of Korea on 14 July.

In northern India, roads and bridges collapsed and houses were swept away as rivers overflowed during heavy monsoonal rainfall and flooding which killed dozens of people. The mountainous state of Himachal Pradesh was badly hit, as were the regions of Punjab, Rajastan and Uttar Pradesh. New Delhi reportedly marked its wettest July day in 40 years, with 153 millimeters (6 inches) of rain falling in one day.

The Japanese Meteorological Agency (JMA) issued heavy rain emergency warnings on Monday for the Fukuoka and Oita prefectures, on Kyushu, the country’s third largest island. A new daily rainfall record of 376.0 mm fell on 10 July at Minousan and 361.5 mm at Hikosan, both in the Kyushu region.

In Northeastern USA, parts of New England suffered serious floods in July.

"As the planet warms, the expectation is that we will see more and more intense, more frequent, more severe rainfall events, leading also to more severe flooding,” said Stefan Uhlenbrook, Director of hydrology, water and cryosphere at WMO.