May Weather

James Russell Lowell said in Under the Willows, “May is a pious fraud of the almanac”. In Phoenix this is only too true! In most sections of the Nation, May brings true spring weather; but in the Desert Southwest, it signals the beginning of the long hot summer.

The average date of the first 100-degree temperature is May 14th. Such a temperature reading has been observed only once as late as June 18th in 1913, and 100-degree temperatures are not spring-like!

The average high temperature is 93.6, and the average low temperature is 63.9. The temperature has reached as high as 114 on the 30th in 1910 and has dipped as low as 39 on the 3rd in 1899. Fortunately, these are rare exceptions.

May signals the beginning of the dry season. The month averages only 0.12 inches of rain and is the driest month of the year. The most rain ever recorded in May was 1.31 inches in 1930. The month averages only one day with 0.01 inches or more of rain, and it has had as many as seven such days, but no more. This happened in 1992. In contrast, there were 14 rainy days in February 1905. Thunderstorms occur on the average of once a month, but few can be seen in the distance on about three other days in the month.

Cloudy days are unusual and occur on only about four days. Sunshine on the average reaches the 93 percent level. Never has any May had less than 79 percent of possible sunshine, which was in 1992.

At the same time, May humidities, like June, are generally extremely low in comparison with those of July and August. Perhaps May should be appreciated more than it is because it is nature’s way of conditioning residents for the steamy summer season of higher temperatures and humidities.