Climate Change Chart of Port Elizabeth, South Africa

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +0.58 °C compared with the earlier reference period. This unweighted mean summarizes the month-by-month averages; it is not a day-weighted annual average and does not mean every month warmed by the same amount. The largest monthly increase was in June, with a difference of +0.98 °C. These are changes in monthly mean temperatures, not daytime maximum temperatures, and the period comparison does not establish a continuous trend.

Changes in rainfall

Mean daily rainfall averaged across calendar months had a difference of -0.30 mm/day compared with the earlier reference period. This unweighted mean describes the aggregate of monthly means, not monthly totals or a day-weighted annual amount, and it does not imply that rainfall decreased in every month. The largest monthly decrease occurred in February, with a difference of -1.20 mm/day; by contrast, the largest monthly increase was in July, with a difference of +0.25 mm/day. Those contrasting monthly changes show why the average should not be read as a uniform month-by-month shift.

Changes in sunshine duration

Mean daily sunshine duration averaged across calendar months had a difference of +0.03 hours/day compared with the earlier reference period. This small positive aggregate difference does not mean sunshine increased in every month: the largest monthly increase was in October, with a difference of +0.66 hours/day, while the largest monthly decrease was in December, with a difference of -0.60 hours/day. These figures describe average daily hours within the relevant months, not total sunshine over a month, and the overall mean is unweighted across calendar-month means.