Besides sending out a heavy friend to skate first, is there a basic guideline, like it being below freezing for a certain period of time? Is it different for different bodies of water?
Thinking back 20 years ago…
I’m fairly certain the town announced when it was safe – 3 or 4 inches thick. However, being a kid at the time, I never listened to them.
Basically, I used to step out on the ice where it was only a foot deep and jump a couple of times. If it didn’t crack, I went out.
I’m sure someone else will be more helpful…
Not sure about a basic guideline, but it will definitely be different for different lakes. A bigger lake will both have more water that needs to be cooled down before it starts freezing, and more currents and wind fetch that can keep water sorta liquid even a bit below the normal freezing temperature. For instance, Lake Superior will probably never be frozen shore to shore, whereas a small pond on its shores (or even a sheltered bay of the same lake) may well freeze to a depth of several feet
I’m not too experienced with this but I would suggest asking a few of the local old timers. Also use some common sense, if it’s just frozen in the last day or so and it’s ~30 degrees I would probably stay away. If it’s been frozen for several days or weeks it would probably be a bit safer. Don’t go out with at least a couple friends (the more the better) to help each other out if the ice isn’t as thick as you thought.
Seeing that you’re in Florida, the short answer is it will NEVER be safe. 
There ARE different guidelines for different types of bodies of water. Moving water, rivers and streams, can almost never be considered safe, because the ice varies in thickness depending on where the current is stronger and weaker. Salt water is also treacherous, even when frozen. As I recall, the salt makes the crystalline structure less stable, as well as lowering the freezing point. For ponds and lakes, IIRC the guideline is if the temperature hasn’t risen above freezing for three weeks, it should be safe (but you still might want to send the fat kid out first). There all kinds of special cases, though. Like, if the ice is covered with snow, it can “rot” even when the temperature is below freezing, if the sun is out.
[slight hijack]
Are most people comfortable going out onto a frozen lake?
Because I never am. Even if I know the ice is thick enough. And I don’t feel that it’s just a phobia. I’m not afraid of water (i.e. drowning) in general. But I can’t ever feel comfortable with the idea that the ground beneath me could give way at any moment and that if it does there’s a 100% chance I’ll sink into freezing cold water and probably drown or freeze to death.
Maybe it’s coming from the land of week upon week of sub-minus 20C temperatures, but I don’t feel uncomfortable on frozen lakes, or even the river ice. We routinely drive across the South Saskatchewan river, which has a pretty substantial current. Before anyone crosses with a vehicle, though people drill test holes to determine the thickness of the ice. It remains mildly dangerous, as currents can eat away at the ice from the bottom, but this doesn’t happen much unless the temperature stays up near freezing for extended periods. The only stories I’ve heard of people putting vehicles through the ice have involved people trying to cross far too early/late in winter.
As for skating on ponds, do be careful. I personally knew a guy who drowned after falling through lake ice. If you’re not sure, check the thickness by drilling or chopping a test hole. Remember that thickness won’t be uniform. If there’s any flow, ice thickness will be inversely proportional to the rate of flow in any given location. And other things being equal, the centre of a pond will have thinner ice than the edges. I’m not sure what minimum recommended thickness for skating is, since ponds freeze to a thickness of a couple feet here, and it just isn’t an issue unless it’s early in winter. It’s normal for ice on smaller ponds to creak and crack and groan while you’re on it, though, so don’t freak out if you hear it doing that, unless the thickness was marginal to begin with, in which case get off of it quickly.
The link posted by Pencil Pusher has lots of information that all looks accurate to me after a quick scan. 2", it says, and recommends tossing rocks and chopping holes. I’d add that jumping up and down aggressively at a point where the water is known to be shallow enough to climb out of isn’t a bad idea.
Around here the simplest way is to check the flag. A red flag means it’s not safe, a yellow flag means skate with caution, and a green flag means it’s safe.
Although I haven’t a clue who puts up the flags, they are always there when the lakes freeze over.
3" plus = avg person is safe
8" plus = avg person w/ snowmobile
14" plus = avg car
These are guidelines that are fairly common. Chances are, in any area where it has a chance of being safe, someone such as the local fire company monitors the ice and puts up notices/flags, as has been mentioned.
Never go alone. Always know the basic survival and rescue tips before venturing onto ice.
If your even asking the OP question, then stay off the ice.
Oh, a common tip: See birds on the lake/pond? You’re probably not safe anywhere near where birds gather, even if it is frozen.
As someone who enjoys ice skating, and always pays attention to security - and still have been through the ice a couple of times, let me try to answer.
Newly frozen ice is very strong. 1cm is enough to hold your weight if it is spread out enough, and you’re not jumping.
When it comes to spring ice, however, 10 cm might break under you.
There is no general rule for thickness <=> strength, and the only way to know for sure is to test. And even testing is not enough to be 100% sure, as the ice can vary a lot over the lake surface.
I have mainly been skiing in Sweden, where we follow the following rules:[ul]
[li]Always have something to test the ice with. (There are special iron-shod wooden (or aluminium) poles.) With this you test the ice before you get out on it, and whenever it changes colour. You strike the ice with the stick, and if it goes through, you know that it’s time to turn back.[/li][li]Always have something to get a grip on the ice. Wet gloves give no grip on ice. There are special plastic (or wooden) grips with metal points that you wear around the neck.[/li][li]Always bring dry clothes. If you go for an unintentional swim, you will be very cold and wet afterwards. Without dry clothes you’re in the risc zone for hypothermia. Dry clothes in a plastic bag in a rucksack also constitute a flotation aid.[/li][li]Always bring a rope, that you can throw to your partner, so that he can help pulling you up. [/li][li]Never go out on the ice alone. - This is the most important![/ul][/li]
In short: Never trust the ice - Always prepare for a quick dip.
If you’re properly equipped a short dip is inconvenient, but not fatal
I’ve gone through half a dozen of times, some intentional - just to test the drill, but most unintentional. It’s really not a big deal, and the pleassure of skating on a wide open lake is definitely worth it!
Just remember - Never go out alone!
As a kid I could usually find a large rock buried in the snow on the shore. I would heave the rock out onto the ice. If the ice could withstand the impact of the rock then I felt it was safe enough to walk on. YMMV, of course.
We had the flag system when I was a kid. However, I notice a LOT of people going through the ice this year. It’s given me the willies and I won’t even entertain the thought anymore. Old age, I guess. It just creeps me out.
As a kid I only went out on the ice after it was “officially” declared safe. Even so, I recall many a time being out on the ice knowing it was safe, but still becoming unnerved as the ice pinged and screamed as it slowly shifted.
If you’ve ever tapped a rock on a long steel I-beam waiting to be installed on a construction site, it’s that sound that sends the heebie-jeebies through you when the ice sounds like that when it shifts – especially when a stress crack zings through the ice between your feet at the same time.
How do you tell it’s safe to skate on a frozen lake?
Wild Ass Guess would be…if you dont fall in…?
Personal safety tip: let someone else test the ice.
Public saftey tip: let the locals test the ice.
Best safety tip: never go on the ice alone.
As some have noticed, I live in Florida (South Florida, as it happens) so the question is mostly academic to me. Thanks for the info, especially that link Pencil Pusher.