I had done an excel sheet with conversions from Deg C to Deg F and printed it for storage in my oddment tray. The key numbers are
-10 deg C is 14 deg F,
0 deg C is 32 deg F,
10 deg C is 50 deg F,
20 deg C is 68 F,
30 deg C is 86 deg F, and
40 deg C is 104 deg F. I did these in my head; there is a formula too. F = C * 1.8 + 32 = C * 9/5 + 32 (if I remember correctly.)

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Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic