Here's one - you have rainfall data for several years.
Code:
#define N_YEARS 10
#define N_MONTHS 12
#define N_DAYS 31  // the max for convenience
int rainfall[N_YEARS][N_MONTHS][N_DAYS];
Then if you had multiple locations, it might be.
Code:
#define N_LOCS 5
#define N_YEARS 10
#define N_MONTHS 12
#define N_DAYS 31  // the max for convenience
int rainfall[N_LOCS][N_YEARS][N_MONTHS][N_DAYS];