Climate of Budapest
As per the 1981–2010 climatological norm, widely used in most other European countries, the climate in Budapest has shifted to an oceanic climate bordering a humid subtropical climate, with averages above 0 °C in the coldest month and above 22 °C in the warmest. The data from the 1991-2020 climatological norm confirm this shift. Winter (December until early March) is the coldest and cloudiest time of year. Snowfall is fairly frequent in most years. The spring months (March and April) see variable conditions, with a rapid increase in the average temperature. Budapest's summer , lasting from June until September, is the warmest time of year. Sudden heavy showers also occur, particularly in May and June. The autumn in Budapest (mid-September until late October) is characterized by less rain than in summer and long sunny days. Seasons. Spring. Spring is characterized by abundant sunshine and scattered showers. The temperature starts to rise markedly in April, highs usually reach the 25 °C mark at the end of the month, though short cold spells with lows in the 0–5 °C zone and ground frost may strike even in mid-May. Summer. In the summer , prolonged heat waves with highs between 32–35 °C interchange with short cooler and wet periods following cold fronts from the West with highs between 18–25 °C. Humidity is usually low in the summer, but may rise during more unsettled weather. In the residential suburbs, humidity is generally lower, leading to lower nighttime temperatures. In the asphalt jungle of Pest, however, temperatures above 25 °C at midnight are not uncommon. Thunderstorms, some of them violent with strong wind gusts and torrential rainfall, are not rare. The highest temperature ever recorded was 40.7 °C on July 20, 2007 . Autumn. Highs can stay above 20 °C until the end of October. Nights get colder and the first frost arrives usually in the second week of October. Short cool spells vary with the Indian summer that can last for several weeks. November brings abundant rain, sometimes snow and a drastic fall in temperature (a 10 °C fall throughout the month). Winter. Winters are variable and unpredictable. Westerly winds bring mild oceanic air with highs between 5–10 °C, almost no frost and scattered rain or snow showers. Depressions moving in from the Mediterranean can bring snowstorms with 20–40  cm falling in a single day, followed by cold air from Russia. Atlantic depressions and south wind can bring unusually warm weather with highs reaching 15 °C even in January. The Siberian High brings most years a sunny but very cold period lasting for a week or two with lows in the −15–20 °C range. Anticyclones with centres above Western Europe produce cold inversion fog with no change in day and nighttime temperatures, they stay around or a bit under 0 °C. The fog can last for weeks. Mediterranean depressions moving above the inversion fog layer can  bring a day or two of freezing rain.