How Many More 110°+ Days?

Updated: 12:00 PM MST July 18, 2008

The heat has returned to the Southwest United States. Thursday, July 17, marked the first 110°+ day in Phoenix in over two weeks. With temperatures Friday expected to surpass 110, this will put the total number of 110°+ days in Phoenix for 2008 at 19. While that is not a record number through this date (record is 24 in 1936), it is about on par with the record-setting pace of 2007 (see Figure 1 below).

Historical count of number of 110 or
greater days in Phoenix through July 18.

Fig. 1. Historical count of number of 110°+ days in Phoenix through July 18.

Fig. 2. Historical count of total number of 110°+ days in Phoenix.

Fig. 3. Correlation between 110°+ days
through July 18 and total 110°+ days.

Based on previous years, it is possible to provide a climatologically driven estimate on how many 110°+ days there may be in total for 2008. The graphic to the right demonstrates the correlation between the number of 110°+ days through July 18 with the final total, based on observations from 1978 through 2007 (note that 1995 was an extreme outlier and removed from the analysis). A fairly good correlation is found. Applying these findings, it is estimated that 2008 may end with 30 110°+ days. Again, it is emphasized that this is based on climatology - weather can and will deviate from climatology.

However, the message remains that there will be more 110°+ days this summer and those in the Southwest should be prepared to deal with this heat. For more information, check out our heat safety page.