If you woke up in the Valley of the Sun yesterday, you probably noticed that the morning air had a bit more "bite" than usual, even for January. People always joke that Phoenix doesn't have a real winter, but tell that to anyone trying to walk their dog at 6:00 AM in a light hoodie. Honestly, the desert has this weird way of tricking you. You see the bright sun through the window and think it’s warm, then you step outside and realize you actually need a jacket.
So, let's get into the specifics of what happened. The high temperature in Phoenix yesterday was 71°F. That might sound like a dream to someone currently shoveling snow in Minneapolis, but for locals, it’s just a standard, crisp Monday in the middle of January. It wasn't a record-breaker. It wasn't a heatwave. It was just... Phoenix being Phoenix.
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Why 71°F in Phoenix Matters Right Now
The temperature hit that 71°F mark right around 2:51 PM. It's a funny thing about the desert; the peak heat usually happens much later in the afternoon than people expect. Most visitors think noon is the hottest part of the day, but the ground takes a while to soak up all that radiation and start pushing it back out.
While the high was 71°F, the overnight low dropped down to 46°F. That is a 25-degree swing in a single day.
This is what scientists call a "diurnal temperature variation," and in Arizona, it’s basically our personality. You spend your morning shivering and your afternoon wondering if you should have worn shorts. If you're a commuter, your car probably saw the 46°F on the dashboard in the morning and by the time you left work, the interior was sitting at a toasty 80°F because of the greenhouse effect through your windshield.
The Breakdown of Yesterday's Conditions
It wasn't just about the raw numbers on the thermometer, though. The vibe of the weather depends a lot on the humidity and the wind, and yesterday was remarkably dry.
- Humidity: The relative humidity bottomed out at a measly 21%. When it’s that dry, 71°F feels significantly cooler than 71°F in a place like Florida or Houston.
- Wind: We had some light breezes coming from the northeast at about 11 mph. It wasn't enough to knock over your patio furniture, but it was enough to make the shade feel chilly.
- UV Index: Even in January, the desert sun is no joke. The UV index hit a 2 yesterday. That sounds low, but if you’re fair-skinned and spent the whole day at a spring training stadium (even though it's technically too early for the games), you probably felt it.
The Urban Heat Island Is Changing Phoenix Winters
There is a lot of talk lately among local meteorologists about how Phoenix is "losing its winter." If you talk to anyone who has lived here since the 80s, they’ll tell you about the "good old days" when you had to scrape frost off your windshield every other morning in January.
That doesn't happen much anymore, especially in the urban core near Sky Harbor Airport.
Why? It’s the concrete.
The Urban Heat Island effect is basically a phenomenon where all the asphalt, buildings, and roads soak up heat during the day and then "bleed" it out slowly all night. This keeps the nighttime lows much higher than they would be in the open desert. Yesterday’s low of 46°F is actually quite "mild" compared to historical averages from forty years ago, even if it felt freezing to you when you were grabbing your mail.
Places like Queen Creek or Buckeye usually stay about 5 to 10 degrees cooler at night than downtown Phoenix because they have more dirt and less pavement. If you live out in the East Valley, you probably saw temperatures closer to 40°F or even the high 30s yesterday morning.
Comparing Yesterday to the Record Books
To give yesterday's 71°F some context, we have to look at what's "normal" for January 12th. Usually, the average high for this time of year is about 67°F. So, yesterday was actually a few degrees above average.
We weren't anywhere near the record high, which was set back in 1943 when it hit a staggering 84°F. On the flip side, the record low for this date was a bone-chilling 24°F in 1913. Imagine 24 degrees in Phoenix—the palm trees would be having a mid-life crisis.
What to Do With This Weather Information
If you're planning your week based on yesterday's 71°F high, you should know that we are in a bit of a warming trend. The forecast for the rest of the week is looking even warmer, with highs creeping up into the mid-70s and potentially hitting nearly 80°F by Wednesday or Thursday.
Basically, winter is taking a coffee break.
For those of you trying to manage a garden or just survive the commute, here is the reality of the current Phoenix climate:
- Dress in layers. It’s the only way to survive a 25-degree temperature swing. A light jacket over a t-shirt is the official uniform of January.
- Water your plants. Even though it’s "cool," the 21% humidity means the air is sucking moisture out of everything. Your potted plants are probably thirstier than you think.
- Check your tires. Large temperature fluctuations cause air pressure to change. If your "low tire pressure" light came on yesterday morning, it’s probably because of that 46°F dip.
The desert is a place of extremes, even when the extremes are as "tame" as 71°F. Yesterday was a perfect example of why we live here: sunshine, clear skies, and a high temperature that makes the rest of the country jealous. Just don't forget your sweater for the morning walk tomorrow.
Next Steps for Your Week:
- Check your irrigation timer: With temperatures hitting the 70s, your desert plants need a steady watering schedule, but don't overdo it—they aren't in summer mode yet.
- Plan outdoor activities for mid-afternoon: The "sweet spot" for warmth is between 1:00 PM and 4:00 PM; before or after that, the lack of sun will make it feel much colder than the recorded high.
- Monitor the local NWS Phoenix feed: They provide the most accurate updates for specific micro-climates in the Valley, which can vary wildly between Scottsdale and Glendale.