Climate Change Chart of Alta, USA

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +1.28 °C compared with the earlier reference period. This is an unweighted average of the monthly means, rather than a day-weighted annual average, and it describes the overall difference between the two periods rather than a steady change over time. The largest monthly increase was in January, at +2.61 °C; this refers to monthly mean temperature, not daytime highs.

Changes in sunshine duration

Mean daily sunshine duration averaged across calendar months had a difference of -0.48 hours/day compared with the earlier reference period. This is an unweighted mean of monthly averages, not a day-weighted annual figure. Monthly changes varied: February had the largest increase, with a difference of +0.22 hours/day, whereas May had the largest decrease, at -1.27 hours/day. The mean summarizes the monthly averages; it does not imply that sunshine changed in the same direction in every month.

Changes in rainfall

Mean daily rainfall had an average difference of -0.02 mm/day across calendar months in the more recent period. This unweighted comparison of monthly means is not a change in monthly rainfall totals or a day-weighted annual average. The monthly pattern was mixed: the largest increase was in January, with a difference of +0.63 mm/day, while the largest decrease was in February, at -1.26 mm/day. These differences describe monthly mean daily amounts, not what happened on every day.

Changes in snowfall

Across calendar months, mean daily snowfall had a difference of 0.00 mm/day at the displayed precision. That unchanged rounded mean does not mean snowfall was absent or that every month's value was unchanged. The monthly differences show some variation: the largest increase was in February, at +0.02 mm/day, while the largest decrease was in January, at -0.05 mm/day. These are differences in mean daily amounts, not monthly snowfall totals.