Hourly weather records reveal the 'true' pace of the changing climate

Small changes in average temperature over extended periods of time can be easy to overlook, but they miss what people actually are actually feeling in their everyday lives. Hourly weather records tell a much sharper story.

Breaking down temperature changes into hourly segments reveals exactly how much time communities in the U.S. and around the world are now spending in deadly cold or dangerous heat conditions.

Using these detailed records, researchers at North Carolina State University (NCSU) found that some regions are losing roughly a week and a half of winter cold each year.

Critical hourly weather patterns

The work was led by Sandra Yuter, a Distinguished Professor of Marine, Earth, and Atmospheric Sciences at NCSU.

Her research focuses on using detailed weather observations to explain how climate shifts show up in everyday conditions people notice.

To run the analysis, the team pulled temperatures from NOAA’s Integrated Surface Database, a database of records from weather stations around the world.

From this source they kept 340 airport stations in the United States and southern Canada, with hourly data available from 1978 through 2023.

Counting hours of heat and cold

Instead of tracking daily highs and lows, the researchers counted how many hours each year stayed below 32°F (0°C) or above 86°F (30°C).

Those cutoffs line up with whether falling water becomes snow or ice, and when people, crops, and livestock start to feel serious heat.

“Trends in threshold exceedance are more easily related to lived experiences than incremental changes to seasonal or annual averages,” said Yuter. 

Here, threshold exceedance, the number of hours when temperatures cross a chosen cutoff, turns abstract warming into changes people can count.

Warming hourly weather patterns

When the researchers mapped their results, winter changes stood out strongly in states east of the Mississippi River and north of 37°N.

Many northeastern and Mid-Atlantic stations now log far fewer hours below freezing than they did during the early years of the record.

On the summer side, stations in Arizona, New Mexico, parts of Nevada, California, and Texas show strong increases in hours above 86°F (30°C).

Those heat hours are likely to bring on heat stress – the strain on bodies and crops from intense heat – for animals and people.

Temperature changes show hotspots

In contrast, much of the north-central United States shows large year-to-year swings but no clear trend in hot or cold hours.

High interannual variability – big jumps from one year to the next – makes it harder to tell whether a place is warming on this metric.

These regional patterns sit on top of anthropogenic climate change – long term warming driven mainly by human activities – that is affecting every continent. 

The latest assessment finds that human influence has warmed the atmosphere, ocean, and land, increasing the frequency and intensity of hot extremes across regions.

Heat exposure reshaping routines

In this study, 86°F (30°C) is not an arbitrary line, because it marks conditions where exposure can strain bodies and farm animals.

Extreme heat kills more than 700 people in the United States each year, and the toll rises when hot hours stack without relief.

For a construction worker or a dairy cow, several hours above that threshold in a single afternoon are more dangerous than a brief spike.

Long stretches of high heat limit how well bodies can cool themselves, raising the chances of dehydration, heat exhaustion, and even heat stroke.

Medical risks from prolonged heat

In cities, the urban heat island – extra warming in built-up city areas compared with nearby countryside – means nighttime temperatures stay elevated after sunset.

If daytime heat hours increase at nearby airports, neighborhoods packed with pavement and little shade can face longer exposure and higher electricity bills.

Public health agencies and city planners can use hourly data to time heat alerts, open cooling centers, and adjust work schedules during dangerous periods.

Because the analysis ties climate trends to hours when people feel heat, it helps decide where shade, water, or breaks can save lives.

Changing energy needs

The same hourly records also reveal how warming winters and hotter summers change energy demand for heating and cooling.

Instead of counting only days, the researchers summed up how far each hour’s temperature was from a comfortable indoor baseline.

They defined heating degree hours, hourly counts of how far temperatures fall below a comfort baseline, as a gauge of building heating needs.

In northern and northeastern locations, heating degree hours are dropping faster than cooling demand is growing, so winter energy use appears to be decreasing.

Utilities and power loads

Familiar degree day indices used by utilities work in a similar way, but they rely on daily averages rather than each hourly reading.

By converting those ideas into degree hours, the team could see subtler shifts, such as whether the hottest hours fall later in the evening.

Where trends are weak but variability is high, including parts of the upper Midwest, utilities plan for swings in both cold and hot years.

That uncertainty means keeping extra capacity in reserve, since a run of cold winters or hot summers could stretch power systems past average expectations.

Preparing for fewer winter freezes

Across the country, evidence lines up with these hourly trends, including the observed shift toward warmer winters and longer growing seasons in many regions.

That climate report finds that the United States has more heat and less cold than a century ago, with changes expected to intensify.

Fewer hours below freezing can change snow totals in Northeast and Midwest – increase road damage from freeze-thaw cycles – and let insects survive winter.

On farms, more frequent warm spells in late winter can coax plants to bud earlier, leaving them exposed if a sharp cold snap returns.

Lessons from hourly weather analysis

Because the study relies on open hourly records from airport stations, local officials can look up nearby trends and connect them to their infrastructure.

A coastal city facing risk might track loss of freezing hours and effects on snowpack, while a desert town watches heat hours during harvest.

Climate statistics can sound abstract, but counting hours above and below thresholds turns them into numbers that match what people remember from their lives.

That connection between data and lived experience makes this analysis useful for motivating climate adaptation in building codes, crop choices, and public health planning.

The study is published in PLOS Climate.

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