Presa Potrerillos Weather Records (MXN00001017)

The fitted trend in annual mean temperature here over 1949 to 2012 is 0.1 C (-0.1 to 0.2) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: 0.1 F (-0.1 to 0.4) per decade. The slope is a straight line fitted to 59 complete years; the brackets give its 95 percent interval.

Across 38 years with a frost, the median last spring frost at Presa Potrerillos falls on 9 February and the median first autumn frost on 30 November, which leaves a median of 303 days between them.

Fitted over all years, the growing season changes by +8.5 days per decade at this station.

A day with at least 42.9 mm (1.7 in) of rain is expected about once in 2 years. A day with at least 107.4 mm (4.2 in) of rain is expected about once in 100 years.

The levels come from a generalised extreme value (GEV) distribution fitted by L-moments to the wettest-day total of each year, 69 years of values from 1943 to 2012.

A return level is an estimate. It is least reliable for the long periods, 50 and 100 years, and for any period longer than the record behind the fit, where the fit has to reach past the largest day actually observed. It is not a forecast.

The largest wettest-day totals in the fit: 146.1 mm (5.8 in) in 1970; 106.2 mm (4.2 in) in 1988; 74.4 mm (2.9 in) in 2002.

One change was suspected in the annual mean temperature of Presa Potrerillos, at 1976. Each is measured against neighbouring stations.

• Relative to 5 neighbouring stations, the station's annual mean temperature from 1976 ran 0.6 C (1.1 F) lower than in the years before (likely change).