What is the amount of snow where the days for storms are 31?
CREATE TABLE "comparison_of_meteorological_data_at_for" (
  "sunshine_hrs_year" text,
  "rain_mm_year" text,
  "snow_days_year" real,
  "storms_days_year" real,
  "fog_days_year" real
);
SELECT SUM("snow_days_year") FROM "comparison_of_meteorological_data_at_for" WHERE "storms_days_year"=31;