As time goes on, it is becoming clearer that Phoenix is growing hotter.
As Phoenix grows hotter, that also creates the question: is Phoenix getting drier?

Using data from a Sky Harbor weather station, I examine the trends in the concrete city from 2007 until 2024.

The first step will be to calculate the averages for the temperatures, from daily averages to monthly averages to yearly averages.

The yearly average temperature calculation is coded in R by:

yearly_avg_temps <- combined_weather_data %>% group_by(Year) %>% summarize(YearlyAvgTemp = mean(HourlyDryBulbTemperature, na.rm=TRUE)) —

The yearly average temperature is calculated using:

\[ \bar{T} = \frac{1}{n} \sum_{i=1}^{n} T_i \]

where:

\(\bar{T}\) is the average temperature

\(T_i\) represents individual daily temperatures

\(n\) is the number of days in a year

The trendline used to analyze warming trends follows the equation:

\[ y = mx + b \]

where: \(y\) is the predicted yearly temperature

\(m\) is the slope of the trendline (rate of temperature increase per year)

\(x\) is the year

\(b\) is the intercept

From the previous graph, there is a clear positive trend. The data confirms that Phoenix is experiencing long-term warming.

The positive trendline in yearly average temperatures suggests that Phoenix is hotter now than it was in 2007.

The increasing temperatures could have significant implications, including longer heatwaves and more extreme summer conditions.

Next, let’s examine how many days over 100 degrees and how many days over 110 degrees there are over the years.

Phoenix is not only having more days above 100°F, but the trendline for days over 110°F is increasing at an even faster rate.

## The slope of the trendline for 100°F+ days is 1.18 days per year.

## The slope of the trendline for 110°F+ days is 1.25 days per year.

The number of extreme heat days in Phoenix is increasing, but 110°F+ days appear to be rising even more dramatically than 100°F+ days.

Even though the numerical difference is small, the impact of more frequent 110°F+ days is far greater. This means there might be more extreme heatwaves, longer-lasting heat events, and increased stress on energy, water supply, and public health.

Last, let’s examine if Phoenix is also becoming drier.

Unlike the increase in extreme heat days, humidity levels have not shown a clear trend over the past 20 years.
- There are spikes and drops in relative humidity, but no consistent increase or decrease.
- The trendline remains mostly flat, indicating that Phoenix’s average humidity levels are stable despite rising temperatures.
- This suggests that higher temperatures are not necessarily causing lower humidity, though further analysis could explore seasonal changes.

The analysis of 20 years of weather data from Phoenix Sky Harbor reveals key trends:

Rising Temperatures:
- The average yearly temperature has steadily increased over time.
- The number of extreme heat days (100°F+ and 110°F+) is increasing, with 110°F+ days rising even faster.

Extreme Heat is Becoming More Frequent:
- Phoenix is experiencing longer, more intense heatwaves.
- The trendline confirms that dangerously hot days are becoming the norm.

Humidity Levels Remain Stable:
- Despite increasing temperatures, humidity has not shown a consistent upward or downward trend. - The fluctuations suggest that other climate factors may be influencing moisture levels.