At about 2 a.m. on Memorial Day weekend last year, in our old tent at Fort De Soto, Dana sat up, peeled her sleeping bag off her legs and said, "Never again above 70." I asked, "Seventy what?" She said, "Look it up in the morning." The dew point that night was 76. None of us slept. Since then, her rule has decided more of our camping than any reservation calendar.
Why the dew point and not the temperature
I'm not a weather expert, so here's the plain version as I understand it. The dew point tells you how much water is in the air. The higher it is, the stickier it feels and the less your sweat dries. It also acts like a floor at night. On a humid night, the temperature doesn't drop much below the dew point. So a night with a dew point of 76 is going to stay somewhere in the high 70s, whatever the forecast low says.
That's why temperature alone kept fooling us. A forecast low of 75 sounds fine for a Florida family. A dew point of 76 means clammy sleeping bags, tent walls beaded with water and kids who kick everything off and still wake up sweaty. A 90-degree day with a dew point of 60 is the opposite. It cools off after dark, and you sleep.
How we use it
Dana checks the National Weather Service forecast for the exact park, not for Miami, about a week out and again two days before we leave. The hourly graph shows a dew point line for each night. This is how those numbers feel to our family in a tent:
- Under 60: sleeping bags zipped, a sweatshirt at breakfast, and coffee tastes better.
- 60 to 65: comfortable. Elkmont in June sat around here, and the kids slept ten hours a night.
- 65 to 70: fans on, a little sticky, still fine.
- Over 70: no tent camping in Florida. That's the rule.
- 75 and up: nobody sleeps. Fort De Soto last year. O'Leno this month.
She also checks the trend. One sticky night in the middle of a dry stretch is survivable. Two in a row, with the fans already struggling, is how a trip turns into a car ride home at 3 a.m.
What it decides for our year
In South Florida, dew points climb to around 70 by the middle of May and mostly stay there until the first real cool front, usually late October or early November. The rule takes Florida tent camping off our calendar for roughly five months. That sounds harsh, but it made our summers simpler. Instead of hoping, we plan around it.
This summer, that meant the mountains. Elkmont in June had lows in the low 60s, and nobody needed a fan. It also meant testing the edges of the rule, and we learned something each time:
- The backyard is an exception. Maya's birthday campout in May had a dew point of 71, but the house was 40 feet away, and anyone could go inside.
- State lines don't count. At Skidaway Island in Georgia in late June, the dew point was 74 and 75 and the tent was 83 at 11 p.m.
- Cold springs don't save warm nights. At O'Leno the weekend before last, the river was 73 degrees, our tent was 84 at 10 p.m., and two fans didn't change that.
Every time we broke the rule, the rule was right. Dana has been gracious about this. Mostly.
The exception still on our calendar
Here's the awkward part. Labor Day weekend, August 30 to September 1, we have two nights booked in the tent at John Pennekamp Coral Reef State Park in Key Largo. I booked it last September at 8 a.m., eleven months out, in a burst of optimism, after the rule already existed. The dew point that weekend will almost certainly be in the mid-70s, and it's the heart of hurricane season.
We're keeping it for now, because Pennekamp is about the water, and the kids have been asking about snorkeling there for a year. Dana agreed on one condition: she gets to call it off that week if the forecast looks wrong, for any reason, no debate. When we booked, we were told that cancelling costs us the reservation fee plus a cancellation fee, about $25 together. That's cheap insurance against a miserable night.
Dana says the rule isn't really about weather. It's about not lying awake at 2 a.m. listening to me say "I think it's starting to cool off." I've said that at least a dozen times since our first trip. It never was.
