Ice Growth, When will it be safe?

Hey Everyone,

Was looking into Ice growth and came upon this article from Outdoor Canada. I will add a link at the bottom but I took the important stuff on here.

To determine freezing degree days and how fast your favourite lake will build up ice, start by taking the average temperature (in degrees Fahrenheit) over the past 24 hours. So, let's say that the daytime high yesterday was 30 F and the night time low was 20 F. This means the average temperature was 25 F. Now, subtract the average temperature (25 F) from the freezing point of water (32 F) and we get 7 freezing degree days.

If the day time high was 20 F, on the other hand, and the night time low was 0 F, the average temperature would have been 10 F, giving us 22 freezing degree days (32 F - 10 F = 22 FDDs).

See how simple it is?

Now, based on the studies that have been done, once a thin sheet of ice has formed on a lake, it will typically increase at the rate of one inch / 15 freezing degree days (FDDS).

So, if we go back to our examples, this means that on the relatively warm day, when there were 7 FDDs, the lake made about one half-an-inch of ice over the 24-hour period. But, on the much colder day, when we experienced 22 FDDs, the lake made about 1.5-inches.

Now, we need to take a couple of important considerations into effect because the formula is based on having a slight to moderate wind speed, no snow on the ground and clear skies. These things all help to pull heat out of the water and accelerate the growth of ice.

we have well over a foot of snow right now and, as most folks are aware, snow provides excellent insulation that slows down the penetration of frost and cold temperatures. In addition, many of our days recently have been calm and overcast. So, when you take these conditions into effect, even with the same number of freezing degree days, the speed at which ice forms is roughly cut in half.

Here is a link to the article

http://www.outdoorcanada.ca/How_Fast_Does_Your_Lake_Make_Ice

Here is a graph for all you visual learners.

I have read this calculation before and I do like it however, it really only applies when your daily averages are consecutively BELOW 32F.

Using the below example of 7 FDD = apprx 1/2 ice formation (based on the calculation and all other variables excluded).

If we have a daily average of 39F the next day and have -7 FDD the ice will not melt 1/2 completely over that time (using the same logic). The relationship is not linear.

E.g. If we have a lake that has 4" ice and a day where, as above, -7 FDD the ice level wont drop to 3.5" after this day as there is enough ice to sustain these temperatures.

All in all, I like these calculations when we consistently have colder than 32F, however just be mindful for this not to be accurate when we have Frozen Degree Days in the negatives (i.e. average temps above 32F).

But great baseline for starting this season! Can't wait to get out.

Very good point. I believe this model requires consistently below freezing temperatures.

This is just a theoretical equation there are a lot of variables that need to be taken into account.

Just thought I'd post to give some food for thought as it was the first time I actually looked into ice growth.

There is more today than yesterday but not as much as tomorrow hope this helps you all understand

all find and dandy but me thinks its easier to just post "Is the ice safe at ......"

It is a great post, I wasn't meaning to take anything away from it! I follow it as well during weeks like these where we know that temps are always going to be below freezing and still open water.

I.e. If I walk out and don't fall through... its ice fishing season!! aha

Yes, you are right. other factors like wind and snow could change all these calculation.
snow will seal the ice and delaying the ice build process.

I dunno how accurate this is. its been -16 for over 24 hours and its been cold for about 7 days now. The ice near me is only 1.5 inches thick, I broke through to measure.

Based on that chart there should be 3" made in the last 24 hours alone.

Graph is in F not Celsius

That chart has been kicked around various ice fishing forums for quite some time, and I believe you are correct, It gives an ice growth rate that I've never ever seen personally.
I prefer to use the chart found here http://idniyra.org/old/articles/ice_sailability.htm
I've found that these numbers match the growth rate quite accurately.

Im aware. -16*C is about 3*F. Which shows the graph saying 3" in 24 hours. Theres only 1.5" near me in about 2 weeks of cold weather.

It is an interesting article, but I call 🐂💩 on most of it!
Every lake and even different parts of every lake form ice at many different rates, there’s depth of snow, wind on the ice/open water, under ice current, springs, and on and on. This time of year, we just have to make sure we don’t leave common sense at home (if we have any to begin with, some aren’t as fortunate as others in that regard), and maybe wait it out a few more days or if we are gonna check out a lake, do it the smart way, not just by hearing something on the internet and figuring “it’s good to go now”.

I call 🐂💩 One of the best I've seen in a while.