I figured out what was happening around mid-June, sitting on my porch with coffee, watching the temperature hit 77°F before noon. My phone buzzed. Amazon suggesting a portable fan. I hadn't searched for any of it. I'd just been sitting there, sweating.

The next day it happened again. 78°F by eleven, and there was a sunscreen ad before I'd even opened my browser. The day after that: 81°F, and my email had three separate promotions for cooling products. I started keeping track. Ice cream ads at 75°F. Humidifier promotions when humidity dropped below 30%. On Thursday it hit 83°F and I got a push notification for roach bait. Turns out cockroaches get more active above 80°F, and retailers know this, and they know you know this, and they're ready with product recommendations before you've even seen the first one scuttle across your kitchen floor.

The platforms are called things like WeatherAds and Weather Alpha. They cost $25 a month to start. They integrate with Google, Meta, TikTok, email, SMS. You set them to activate ads only when conditions are optimal. Aperol runs billboards only above 66°F. Molson Coors triggers Facebook ads at 23°C and sunny. Pantene saw a 28% sales increase running humidity-triggered ads for anti-frizz products. When pollen count spikes, the antihistamine ads arrive, followed by indoor activity suggestions, air purifiers, comfort purchases for people who can't go outside without their sinuses staging a revolt.

Walmart's AI assistant can check the weather at your destination and suggest outfits. The corporate language calls it "predictive weather intelligence" that helps brands connect with consumers when conditions create the "perfect physical and emotional context." The perfect context being: you're hot, you're miserable, your judgment is impaired by heat stress, and they're ready with a $39.99 solution.

That's when they start.

I didn't buy the fan. But I looked at it. Clicked through to read reviews. Checked the price. Added it to my cart to "save for later." I knew what was happening and I did it anyway. The algorithm doesn't care if you know what it's doing. I was hot. That was enough.

Electronic shelf labels in grocery stores are now linked to weather data, enabling real-time price adjustments. Ice costs more when it's hot. The labels make it easier. The system processes the data in milliseconds—temperature, inventory, your browsing history, whether you're the kind of person who buys ice when it's expensive or waits until it cools down. Amazon changes prices millions of times per day. The average product's price shifts every ten minutes. Weather is just one input. But it's a durable one. You can't opt out of weather. You can't clear your weather cookies.

I thought about calling my sister. She lives in Phoenix, moved there in 2019 for a nursing job, stayed because she liked the dry heat. I wanted to ask if she'd noticed the pattern, if her phone had been doing the same thing. But I knew how it would sound. She would've said yeah, obviously, or that's not new, or I'm busy can we talk later. All of which would've been true. Also true: weather influences approximately $1 trillion in global retail sales annually, and in regions experiencing heatwaves for over three weeks, air conditioner sales swell by 150-200%, and the algorithms saw it coming, and they were ready, and my sister probably bought an air conditioner this summer, and probably saw the ad right when her body was most likely to click.

By evening it was 84°F. The box fan showed up again in my recommendations. Different brand this time, $10 cheaper, four-star reviews, ships tomorrow. I'd been seeing it for three days. The price kept changing. I kept not buying it. But I kept looking. Kept reading reviews. Kept checking if the price had dropped. The algorithm was patient. It knew I'd get hotter. It knew the forecast.

I sat there watching the temperature climb. My phone buzzed. Cooling sheets. Popsicle molds. Window unit, marked down, limited time offer. The algorithm doing what it does. Me sitting there sweating, scrolling. The temperature kept rising. The ads kept coming. I didn't buy anything that day, but the fan was still in my cart. By the weekend it was supposed to hit 90°F. I figured I'd find out.