Tucson has five seasons: Two major seasons, summer and winter, plus three minor seasons: autumn, spring, and monsoon season.

Summer is characterized by low humidity, clear skies, and daytime high temperatures that exceed 100 degrees Fahrenheit. The average overnight temperature ranges between 69F and 74F.

Monsoon season typically begins in July, but can begin anytime from June to August. During monsoon season the humidity is much higher than the rest of the year. This period begins with clouds building up from the south in the early afternoon followed by intense thunderstorms and rainfall, which can cause flash floods. Large areas of the city do not have storm sewers, so monsoon rains flood the main thoroughfares but usually only for a few hours. A few underpasses in Tucson have "feet of water" scales painted on their supports to indicate whether they can be safely forded by an automobile during a rainstorm. The evening sky at this time of year is often pierced with dramatic lightning strikes.

Autumn lasts from late October to November or December. It is much like summer, and similarly dry, with days above 100 degrees typical into early October. Average daytime highs of 84F, with overnight lows of 55F, constitute typical fall weather.

Winters in Tucson are mild relative to other parts of the United States. Daytime highs in the winter range between 64F and 90F, with overnight lows between 30F and 44F. Although rare, snow has been known to fall in Tucson, usually a light dusting that melts within a day.

Spring begins in late February or March, and is characterized by rising temperatures and several weeks of vivid wildflower blooms. Daytime average highs range from 72F in March to 88F in May with average overnight lows in March of 45F and in May of 59F.

Demographics-

As of the census GR2 of 2000, there were 486,699 people, 192,891 households, and 112,455 families residing in the city. The population density was 965.3/mi(2,500.1/km). There were 209,609 housing units at an average density of 415.7/mi (1,076.7/km). The racial makeup of the city is 70.15% white, 4.33% black or African-American, 2.27% Native American, 2.46% Asian, 0.16% Pacific Islander, 16.85% from other races, and 3.79% from two or more races. 35.72% of the population were Hispanic of any race. The Native American inhabitants in the area include primarily Tohono O'odham (formerly called the Papago), living in the city, on the nearby San Xavier reservation, and in the Tohono O'odham Nation, who may be descendants of the prehistoric inhabitants, as well as 6,800 Yaqui, living in the city (largely in the Old Pascua and Barrio Libre neighborhoods), on the nearby Pascua Yaqui reservation, and in the Yoem Pueblo in the town of Marana.

There were 192,891 households out of which 29.0% had children under the age of 18 living with them, 39.7% were married couples living together, 13.8% had a female householder with no husband present, and 41.7% were non-families. 32.3% of all households were made up of individuals and 9.3% had someone living alone who was 65 years of age or older. The average household size was 2.42 and the average family size was 3.12.

In the inner-city, the population has 24.6% under the age of 18, 13.8% from 18 to 24, 30.5% from 25 to 44, 19.2% from 45 to 64, and 11.9% who were 65 years of age or older.

The median income for a household in the city was $30,981, and the median income for a family was $37,344. Males had a median income of $28,548 versus $23,086 for females. The per capita income for the city was $16,322. About 13.7% of families and 18.4% of the population were below the poverty line, including 23.6% of those under age 18 and 11.0% of those age 65 or over.