Data Dashboard – Reuters Climate Monitor – How today’s temperatures compare to the historic average – Updates daily – The Reuters Climate Monitor shows where temperatures are unusually hot or cold in real time by comparing today’s conditions with what was typical in the past. We start by establishing what normal used to look like. Using hourly temperature records from the European Centre for Medium-Range Weather Forecasts’ ERA5 reanalysis dataset, we calculate the typical temperatures for each of roughly one million grid squares covering the Earth’s surface for each day of the calendar year. The normal values are drawn from a 30-year window spanning 1961 to 1990, a standard reference period used by climate scientists. To reduce noise, each day’s normal temperatures are calculated using a 31-day rolling window — 15 days on either side of that calendar date — across all 30 years of data. To compare today’s conditions, we download the latest temperature forecast from the ECMWF’s HRES forecasting system, which covers the same global grid. Because HRES and ERA5 are generated by different models, they can produce slightly different readings for the same conditions. To address the issue, we apply a statistical correction — calculated by comparing the two models over a multi-year overlap — to put them on equal footing. With the datasets aligned, we subtract the historical normal from today’s forecast for each grid square. The result is the anomaly reported by our map, which shows how much hotter or colder today’s high temperature is compared to what used to be the typical high on that date. Forecast highs are calculated over UTC calendar days, which may span parts of two local dates depending on location.