If you store your rain-fall-data in an array, r_f for rain_falls, with n_t rows and n_stations columns you could easily do thing like:
n_t = 37; % just to mock up an
n_s = 6; % an illustrating
r_f = 5*randn(n_t,n_s).^2; % example
rf_threshold = 1;
subplot(1,3,1)
imagesc(r_f) % the rainfall
xlabel('station')
ylabel('day-number')
axis xy
subplot(1,3,2)
imagesc(r_f>rf_threshold) % illustrating days with rainfall larger than selected threshold
axis xy
subplot(1,3,3)
stairs(sum(r_f>1,2),1:n_t) % stations with more than threshold rainfall at each day
grid on
idx_all = find(all(r_f>rf_threshold,2); % index to days with all stations with enough rain
idx_5 = find(sum(r_f>rf_threshold,2)>=5); % index to days with 5 or more stations with enough rain
HTH
