From Longman Dictionary of Contemporary English(come) rain or shine(come) rain or shinespokenWEATHER whatever happens or whatever the weather is like Don’t worry. We’ll be there – rain or shine. → rain
Examples from the Corpus
(come) rain or shine• Every morning at about 5am, come rain or shine, James Zarei leaves his South Croydon home on his morning run.• Scores of rambling and cycling clubs headed remorselessly for the Dales each weekend, come rain or shine.• Burrow runs two miles, rain or shine, everyday.• The working week began every Monday, rain or shine.• He seldom drinks alcohol, never touches drugs, and runs six miles every morning, rain or shine.• I kid you not: each year rain or shine, Californian Poppy. 