Climate Change Chart of Vientiane, Laos

Overview of climate changes

Changes in sunshine duration

Mean daily sunshine duration, averaged across calendar months, shows a difference of -0.49 hours/day compared with the earlier reference period. This is an unweighted average of monthly means, not a day-weighted annual average; it describes the overall monthly-average comparison, not the change in every month. The largest monthly decrease in mean daily sunshine was in July, with a difference of -1.80 hours/day. In November, the largest monthly increase was much more modest, at a difference of +0.27 hours/day. These are monthly differences in average daily hours, not measures of sunshine on individual days.

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +0.60 °C compared with the earlier reference period. This is an unweighted average of monthly means, not a day-weighted annual average, and it describes the aggregate rather than every month. The largest monthly increase was in November, at a difference of +1.55 °C. By contrast, February had the largest monthly decrease, a difference of -0.44 °C. These are monthly mean temperatures, not daytime maximum temperatures, and identify the strongest changes in each direction rather than a uniform shift across the year.

Changes in rainfall

Averaged across calendar months, mean daily rainfall has a difference of +0.37 mm/day compared with the earlier reference period. This unweighted average of monthly means is not a day-weighted annual average or a monthly rainfall total, so it summarizes the month-by-month averages rather than indicating that rainfall increased in every month. The largest monthly increase in mean daily rainfall occurred in July, with a difference of +4.42 mm/day. The largest decrease was in April, at a difference of -1.20 mm/day. These contrasting monthly changes show why the average difference should not be taken to describe every month's rainfall.