Johannesburg recorded its first confirmed snowfall for almost 26 years overnight as temperatures dropped below freezing in South Africa's largest city, grounding flights at its main airport.

The heaviest falls were over the southern suburb of The Hill, where four inches of snow fell, said Venetia Magane, a forecaster at the South African Weather Service in Pretoria. Temperatures in the city fell to minus 1 degree Celsius (30.2 degrees Fahrenheit) during the night, she added.

''It started last night and by this morning everything was covered,'' Bernice Hodkinson, a beautician in the southern suburb of Mondeor, said in a telephone interview. ''The kids are making snowballs in the veld, it's beautiful.''

Snow last blanketed Johannesburg for a single day on Sept. 11, 1981. The city's average minimum temperature for June over the past 47 years is 4 degrees Celsius, according to data provided by the South Africa Weather Service. This year's average minimum is 4.7 degrees compared with 0.7 degrees in 1968, the coldest on record.

Flights leaving O.R. Tambo International airport were delayed for as long as three hours this morning while ice was cleared from runways and snow removed from aircraft, the South African Press Association said, citing Tasniem Patel, spokeswoman for Airports Company South Africa Ltd.

Light snowfall was also recorded in Pretoria, the capital, which last had snow on June 11, 1968, the newswire said.