In March and April the days are mostly sunny and warm and the nights are cool. The average highs range from 70 to 80 degrees Fahrenheit with lows generally are in the 40s and 50s. There can be cold snaps in the spring, and spring showers may occasionally interrupt the long succession of clear, sunny days.
Summers are hot. May high temperatures reach 85 and climb to over 100 degrees in June. Highs in the summer can be above 110 degrees, but the nighttime and early morning temperatures are usually no more than 70. Residents plan their summer activities early in the day to beat the midday heat, which in any case feels less intense than it does in some other places because of the low humidity. The average daytime relative humidity during the summer months is below 15 percent.
Tucson's "fifth season" is the rainy period from late June until September. Daytime temperatures are still high at this time of the year, but thunderstorms often cool things off. Unique weather patterns bring moisture from the Gulf of California to the normally dry air. Mornings are typically clear with increasing clouds in the early afternoon leading to late afternoon or evening storms. These often include spectacular displays of wind, torrential rain and lightning. More than half of Tucson's rain comes during the monsoon season, sometimes in short bursts that cause localized flooding.
In October and November the weather again turns mild as the air dries out following the monsoon rains. As in spring, the days are usually warm and the nights cool. The average highs move from the 90s into the 70s as the lows drop back to the 50s and then the 40s.
December through February is the season that brings the most visitors to Tucson. The days are usually warm and mild but nights can sometimes be cold. Highs usually range up to the 60s and the low 70s with average low temperatures in the 30s and 40s. In outlying areas and higher elevations there can be hard freezes. Most days are clear and dry but a few inches of rain are likely to fall during the winter months.
