Belfast weather history — trends, records & warming

12 of the last 23 days were warmer than the historical average for that date. Average difference: +1.2°C.

Each bar is one day, from morning low to afternoon high. Warm-colored bars are days whose mean ran above average; cool bars ran below. The dot inside the bar is the daily mean. The shaded band is the typical 10–90% range expected for that date. Average = the day's mean temperature averaged across every year of record (1940–2026) for that calendar date.

One dot per year — the mean temperature on this calendar date. Dots are warmer or cooler than the long-term average (dashed line); the shaded band is the typical 10–90% range, and the highlighted dot is today's forecast. Based on ERA5 reanalysis — modelled estimates, not station readings.

Annual mean shifted from 1940–1949 to 2016–2025 by +0.7°C.

Each vertical stripe is one year. Color encodes how much that year's annual mean differed from the long-term average. Average = each year's annual mean compared to the average of all years (1940–2026). cooler ← → warmer

Long-term trend: +0.11°C per decade.

One point per year — the temperature averaged across the whole year. The dashed line is the least-squares long-term trend. Based on ERA5 reanalysis — modelled estimates, not station readings.

Dec–Feb is warming fastest: +0.16°C per decade.

Each faint line is one three-month period's average per year; the bold dashed line is its long-term trend. Different parts of the year often warm at different rates. Based on ERA5 reanalysis — modelled estimates, not station readings.

Days ≥ 25°C per year: 0.0 early in the record → 0.5 recently. Frost days: 16 → 7.

Thin lines are raw yearly counts; thick lines are the smoothed trend that removes year-to-year noise. The hot-day threshold is auto-picked per city so the line actually moves. Average = a centered 5-year rolling average to smooth weather noise.

All-time high in 2018, all-time low in 2010: 25.8°C / -9.6°C.

One point per year — the single hottest and coldest day recorded that year.

~938 mm/year on average. Last decade ran +4% vs that average.

One bar per year of total rainfall. Dashed line is the long-term average. Average = the average annual rainfall across every year of record (1940–2026).

Each tiny square is one calendar day across the full record — ~30,000 days per city. Use the mode switch above the chart: Anomaly colors each day by how far it ran from the historical average for that date (red = warmer, blue = cooler), Daily mean temp shows the absolute mean temperature for the day (useful to see seasons and heatwaves), and Precipitation shows daily rainfall (useful to spot wet/dry seasons and droughts). Average = the long-term average for that calendar date (1940–2026).

July is the warmest month, January the coolest — a yearly swing of 10°C.

Each bar is the average daily low → average daily high for that month. Color shifts cool→warm by month temperature. The dot is the monthly mean. Average = each month's value averaged across every year of record (1940–2026).

Wettest month: October (~88 mm). Whole year averages ~938 mm of rain.

Average total millimetres of rainfall in each calendar month, across the full record.

Average daily peak wind at 10 m, by month.

Average daily incoming solar energy in megajoules per square metre — a measured proxy for how sunny the month is.

Typical conditions for each month, averaged across the full record (since 1940). Sun is the mean hours of bright sunshine per day; daylight is the time from sunrise to sunset. Record high/low are the most extreme values in the ERA5 dataset (modelled since 1940), so they can differ from official weather-station readings. The green dot marks the best time to visit — the months whose average afternoon high sits closest to a comfortable 23°C.

Best time to visit (mildest weather): June–September