Climate Change Chart of San José, Costa Rica

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +1.12 °C compared with the earlier reference period; this is an unweighted average of the monthly means, not a day-weighted annual average or a measure of daytime highs. The largest monthly increase was in January, with a difference of +1.43 °C. That monthly result highlights one particular change and should not be read as applying to every month or as evidence of a continuous trend.

Changes in rainfall

Mean daily rainfall averaged across calendar months shows a difference of -0.78 mm/day compared with the earlier reference period. This unweighted comparison of monthly means is not a day-weighted annual average, and it describes daily amounts rather than monthly totals. The largest monthly decrease was in July, with a difference of -4.23 mm/day, while the largest monthly increase occurred in May, with a difference of +2.02 mm/day. These contrasting monthly differences show why the overall mean does not describe every month’s change.

Changes in sunshine duration

Mean daily sunshine duration, averaged across calendar months, shows a difference of +0.60 hours/day compared with the earlier reference period; this is an unweighted mean of monthly averages, not a day-weighted annual figure. The largest monthly increase was in July, with a difference of +1.37 hours/day, whereas the largest monthly decrease was in April, with a difference of -0.43 hours/day. The overall mean and these month-specific results describe separate aspects of the comparison: the average across months does not imply the same change in each month.