Climate Change Chart of Salem, USA

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +0.74 °C compared with the earlier reference period; this is an unweighted comparison of monthly means, not a day-weighted annual average or a statement about every month. The largest monthly increase was in January, with a difference of +2.19 °C. By contrast, December had the largest monthly decrease, a difference of -0.37 °C. These monthly means describe average temperatures, not daytime maximum temperatures.

Changes in rainfall

Averaged across calendar months, mean daily rainfall had a difference of +0.10 mm/day in the more recent period; this unweighted comparison of monthly means does not imply that rainfall increased in every month. The clearest monthly contrasts went in opposite directions: January had the largest increase, a difference of +0.82 mm/day, while November had the largest decrease, a difference of -0.88 mm/day. These figures describe mean daily amounts rather than monthly rainfall totals, and the period comparison does not indicate a continuous change between the reference periods.

Changes in sunshine duration

Mean daily sunshine duration averaged across calendar months had a difference of -0.27 hours/day compared with the earlier reference period, an unweighted summary of monthly means rather than a day-weighted annual measure. The monthly pattern was not uniform: June recorded the largest increase, a difference of +0.30 hours/day, whereas January recorded the largest decrease, a difference of -0.86 hours/day. These contrasts describe average daily sunshine for the relevant months; they do not establish a continuous trend between the two periods.

Changes in snowfall

Averaged across calendar months, mean daily snowfall had a difference of +0.17 mm/day in the more recent period. This is an unweighted comparison of monthly means, not a day-weighted annual average, and does not mean that every month changed in the same direction. The largest monthly increase occurred in February, with a difference of +1.68 mm/day, while January had the largest decrease, a difference of -2.07 mm/day. The figures are mean daily snowfall amounts rather than monthly totals; the period differences describe the endpoints only, not a continuous trend.