Climate Change Chart of Sintra, Portugal

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +0.54 °C compared with the earlier reference period; this is an unweighted average of the monthly means, not a day-weighted annual figure or a measure of daytime highs. The largest monthly increase was in December, with a difference of +1.56 °C. By contrast, June had the largest monthly decrease, a difference of -0.50 °C; these monthly contrasts show that the overall mean does not describe every month.

Changes in sunshine duration

Mean daily sunshine duration, averaged across calendar months, had a difference of -0.30 hours/day compared with the earlier reference period. The figure summarizes unweighted monthly means rather than a day-weighted annual average. The largest monthly decrease was in April, with a difference of -0.64 hours/day. In December, the largest monthly increase was much more limited in direction and scale, at a difference of +0.09 hours/day; neither observation means that every day in those months followed the monthly average.

Changes in rainfall

Averaged across calendar months, mean daily rainfall had a difference of +0.16 mm/day in the more recent period. This is an unweighted comparison of monthly means for daily rainfall, not a comparison of monthly rainfall totals. The largest monthly increase occurred in April, at a difference of +0.83 mm/day, while January recorded the largest monthly decrease, a difference of -0.81 mm/day. These month-specific changes qualify the modest positive mean difference: it does not imply that daily rainfall increased in every month.

Changes in snowfall

Averaged across calendar months, mean daily snowfall had a difference of -0.03 mm/day. This small decrease describes the unweighted monthly means at the displayed precision; it does not establish that snowfall was absent or unchanged in every month. The largest monthly decrease was in January, with a difference of -0.29 mm/day. This is a change in mean daily snowfall, not a monthly snowfall total, and it should be read as a period comparison rather than a continuous trend.