Merthyr Tydfil Temperature by Month

The average annual maximum temperature in Merthyr Tydfil, Glamorgan, United Kingdom is 14°C (57°F), with daytime highs ranging from 8°C (46°F) in January to 20°C (68°F) in July. This page covers monthly averages, day-night differences, and how Merthyr Tydfil compares to cities worldwide.

Visitors to Merthyr Tydfil can expect significant temperature changes throughout the year. Nighttime temperatures also vary widely, ranging from 12°C (54°F) in July to 2°C (36°F) in January.

The chart below illustrates the average maximum day and minimum night temperatures in Merthyr Tydfil by month:

The minimum temperature is often recorded between 4 AM and 6 AM, while the highest temperature is usually reached at 3 PM, when the sun's heating effect is strongest. July, the warmest month, gets 202 hours of sunshine.

The chart below shows the average temperature throughout the year:

Merthyr Tydfil's average annual maximum temperature is 14°C (57°F). To put that in context, here's how it compares to a few well-known destinations:

Rome, Italy averages 20°C (68°F) annually, with reliably warm summers and comfortable winters.

Zermatt, Switzerland averages just 4°C (39°F) annually due to its altitude, with very cold winters and cool summers even at its warmest.

Osaka, Japan averages 22°C (72°F) annually, with hot humid summers, mild winters, and pleasant spring and autumn seasons.

Tokyo, Japan averages 21°C (70°F) a year, with hot summers, cool winters, and a well-defined cherry blossom spring.

Temperature alone doesn't tell the whole story, humidity plays a big role in how warm or cold it actually feels. High humidity in summer makes the heat feel more intense, particularly once temperatures climb above 25°C. In winter, the same humidity can make cold air feel sharper than the thermometer suggests.

In the cooler months, when temperatures drop below 10°C, high humidity makes the cold feel more cutting than it would in dry conditions.

In Merthyr Tydfil, January is the coolest month, with average highs of 8°C (46°F) and humidity around 89%, considered very high. For a full picture, see our humidity page.

Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.

The readings come from a range of sources, land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.

Seasonal temperature shifts influence more than just how warm it feels, they also drive changes in rainfall, cloud cover, and wind patterns throughout the year.

Warmer air holds more moisture, which tends to mean heavier or more frequent rain during the warmer months. When temperatures drop in winter, any precipitation that does fall is more likely to come as snow or sleet, though in Merthyr Tydfil this rarely lasts long on the ground.

For more on Merthyr Tydfil's weather, including monthly rainfall, sunshine hours, and humidity, visit our Merthyr Tydfil climate page.