What Temperature Does Hummingbird Nectar Freeze, and Does 3:1 Help?
Worked from the published sucrose freezing table: 4:1 grows its first ice at 29.7 °F, is half ice by 27.3 °F, and a 3:1 mix buys you less than one degree.
The short answer
- Standard 4:1 nectar (1 cup sugar to 4 cups water) starts to freeze at about 29.7 °F, which is 1.3 °C below zero.
- A 3:1 mix starts at about 28.9 °F. Adding a third more sugar buys 0.8 °F, a margin no overnight forecast is precise enough to use.
- Nectar does not freeze at one temperature. Ice forms from the water, the syrup left behind gets stronger, and 4:1 is about half ice at 27.3 °F. That is where the 26 to 27 °F figures on other sites come from.
- Wind chill does not freeze nectar. A feeder cannot cool below the air temperature, so plan on the forecast low, not the feels-like number.
- Keep 4:1 all year. When the low is below about 30 °F, swap two feeders at dusk and first light instead of strengthening the mix.
Standard 4:1 hummingbird nectar starts to freeze at about 29.7 °F, 1.3 °C below zero. A 3:1 mix starts at about 28.9 °F. The stronger mix buys you 0.8 °F, which is why this site keeps 4:1 all year and handles frost by swapping feeders instead of adding sugar.
The figures in circulation run from 26 to 29 °F. The real numbers can be worked out from a published table in a few lines, and the working also shows where the others came from.
The working, from sugar in a cup to degrees on a thermometer#
How much sugar is in the mix. USDA FoodData Central lists one cup of granulated sugar at 200 g. A US cup is 236.6 mL, so four cups of water weigh about 946 g. The household batch on the hummingbird nectar recipe page is therefore 200 g of sugar in 946 g of water: 21.1 g of sugar per 100 g of water, or 17.4% sugar by weight.
What that much sugar does to the freezing point. The University of Guelph's food science department publishes a table of freezing point depression for sucrose solutions, given in grams of sucrose per 100 g of water, with data from Leighton (1927), originally derived from Pickering (1891). The table puts 21 g at 1.29 °C of depression and 24 g at 1.47 °C. Interpolating to 21.1 g gives 1.30 °C, so 4:1 nectar begins to freeze at 1.3 °C below zero, which is 29.7 °F.
The same arithmetic for every ratio people actually use:
| Mix (water to sugar, by volume) | Sugar per 100 g water | Sugar by weight | Starts to freeze (°C below zero) | Starts to freeze |
|---|---|---|---|---|
| 6:1 (oriole strength) | 14.1 g | 12.3% | 0.85 | 30.5 °F |
| 5:1 | 16.9 g | 14.5% | 1.03 | 30.2 °F |
| 4:1 (standard) | 21.1 g | 17.4% | 1.30 | 29.7 °F |
| 3:1 | 28.2 g | 22.0% | 1.74 | 28.9 °F |
| 2:1 | 42.3 g | 29.7% | 2.62 | 27.3 °F |
All five fit inside a 3.2 °F band: sugar at feeding strength is a weak antifreeze. The 6:1 row is the weaker mix used in oriole feeders, and the nectar calculator gives batch quantities, but only the 4:1 row is one this site recommends for hummingbirds.
Why other sites say 26, 27, 28 or 29 °F#
Nectar does not freeze at one temperature. When sugar water freezes, the ice that forms is nearly pure water, so the syrup left behind gets stronger and its own freezing point drops. The Guelph document uses exactly this method to build a freezing curve for ice cream mix: take out the frozen share of the water, recalculate the concentration, read the new temperature off the table. Applied to plain nectar it gives this:
| Share of the water frozen | 4:1 nectar | 3:1 nectar |
|---|---|---|
| First crystals | 29.7 °F | 28.9 °F |
| A quarter | 28.9 °F | 27.8 °F |
| Half | 27.3 °F | 25.5 °F |
| Three quarters | 21.5 °F | 17.2 °F |
Read the 4:1 column against the numbers in circulation and the disagreement sorts itself out:
- 29 °F is close to right for the first ice.
- "Slushy at 27 °F" is a good description of a 4:1 feeder that is half frozen.
- 26 to 27 °F as the freezing point is wrong for 4:1. It describes a feeder well into slush. The only common mix that grows its first crystal there is 2:1, twice the standard strength.
- 28 °F sits between the first crystal and a quarter ice. We could not find a source for it.
What 3:1 actually buys you#
Less than one degree where it matters. At first ice, 3:1 is 0.8 °F behind 4:1. At half ice the gap has grown to 1.8 °F, and at three-quarters ice to 4.3 °F. The gap widens only once both feeders are already mostly slush.
Put that against a real night. If the low is 25 °F, a 4:1 feeder can be about two-thirds ice and a 3:1 feeder just over half. Both are slush and both need swapping at dawn. The only nights on which 3:1 stays clear and 4:1 does not are nights with a low between 28.9 and 29.7 °F, and even then the 4:1 feeder is at most a quarter ice. No overnight forecast is accurate to 0.8 °F, so there is no night you could plan around that window, and the dawn swap covers it anyway.
The reasons to keep 4:1 year round are on the recipe page, and other ideas that do not survive a close look are on bird feeding myths.
Which temperature to plan against#
Use the forecast air temperature. The National Weather Service states that wind chill applies only to people and animals: wind cools an object to the air temperature faster, but never below it. A feeder in a 31 °F gale with a single-digit wind chill is still above 4:1's freezing point.
A small volume of liquid reaches air temperature sooner than a large one, so nectar in the ports and in a shallow saucer feeder gets there before the middle of a full bottle. A glass reservoir can crack when it freezes hard, see glass vs plastic hummingbird feeders.
A rule for tonight, by the forecast low#
| Forecast low | What happens to 4:1 | What to do |
|---|---|---|
| 30 °F or above | No ice can form | Nothing. Leave the feeder up |
| 28 to 29 °F | Up to about 40% ice | Check the ports at first light; swap if they are blocked |
| 25 to 27 °F | About half to two-thirds ice | Swap at dusk and again before first light |
| Below 25 °F | More than two-thirds ice | Swap at dusk and first light; insulate or warm the reservoir if the day stays below freezing |
The dusk and dawn swap is the routine described on hummingbird feeder timing: keep a second feeder indoors at room temperature, take the cold one in at dusk and hang the warm one before first light. A hummingbird comes out of a cold night needing to feed within minutes of dawn, and that first visit is the one the swap protects. The wider cold-weather picture for the rest of the yard is on winter bird feeding.
Where these numbers stop applying#
- Plain white sugar only. The Guelph table is for sucrose. Nectar made with anything else is not covered by it, and commercial mixes vary in what they contain, one more point in the homemade vs store-bought nectar comparison.
- Measured by volume. Four parts water to one part sugar by weight is 25 g per 100 g of water, and it starts to freeze near 29.2 °F instead of 29.7 °F. Half a degree, so it changes nothing in the table above.
- Equilibrium, not timing. The table says how much of the water can be ice at a given temperature. It says nothing about how long that takes, so read it as the worst case for a night that holds at its low.
- Air temperature at the feeder. A forecast low is for the weather station. If your feeder hangs in a low, sheltered corner, a thermometer beside it will tell you more than the forecast.
Who needs this, and when#
In most of the East the question comes up on a few frosty nights at each end of the season, while late Ruby-throated Hummingbirds pass through. On the Pacific coast Anna's Hummingbird is resident, and the swap becomes a nightly winter routine. The months are on the bird feeding calendar.
Cold does not suspend hygiene. Project FeederWatch notes that mold and fungi readily grow in sugar water, so nectar that freezes and thaws still needs changing and the feeder a proper wash. The feeder cleaning schedule sets the interval, and designs that are easy to swap and scrub are on hummingbird feeders.
Frequently asked questions#
What temperature does hummingbird nectar freeze at?
Standard 4:1 nectar, one cup of white sugar in four cups of water, begins to freeze at about 29.7 °F (1.3 °C below zero). That is the temperature at which the first ice crystals can form. It does not turn solid there: as water freezes out, the remaining syrup gets stronger and harder to freeze, so a 4:1 feeder is roughly half ice at 27.3 °F and three-quarters ice at about 21.5 °F.
Does a 3:1 mix stop hummingbird nectar freezing?
Not in any way you can use. A 3:1 mix starts to freeze at about 28.9 °F against 29.7 °F for 4:1, a gain of 0.8 °F. At half ice the gap is 1.8 °F. A night that bottoms out at 25 °F takes both mixes well into slush, and the only lows at which 3:1 stays clear while 4:1 does not fall in a window under one degree wide. Swapping two feeders protects the birds; a third more sugar does not.
Why do some sites say nectar freezes at 27 °F?
Because they are describing a feeder that is already half frozen. Sugar water freezes over a range, not at a point. A 4:1 mix grows its first ice at about 29.7 °F and reaches half ice near 27.3 °F, which is exactly when someone looks at the feeder and calls it frozen. The only common mix that starts to freeze near 27 °F is a much stronger 2:1.
Will wind chill freeze my hummingbird feeder?
No. The National Weather Service is explicit that wind chill applies only to people and animals: wind cools an object to the air temperature faster, but never below it. A feeder in a 31 °F wind with a single-digit wind chill stays above 4:1's freezing point. Use the forecast low, and a thermometer near the feeder if you have one.
Does it matter if I measure 4:1 by weight instead of volume?
Slightly. The site recipe is by volume, which works out to about 21 g of sugar per 100 g of water. Four parts water to one part sugar by weight is 25 g per 100 g, a stronger mix that starts to freeze near 29.2 °F instead of 29.7 °F. The difference is half a degree, so it changes nothing about how you run a winter feeder.
Sources and further reading
- Freezing Point Depression of a Mix University of Guelph, Department of Food Science Freezing point depression of sucrose solutions in g per 100 g water (Leighton 1927, from Pickering 1891) and the freezing curve method
- Sugars, granulated (FDC ID 169655, SR Legacy) USDA FoodData Central One cup of granulated sugar weighs 200 g
- Understanding Wind Chill National Weather Service Wind chill cools objects to the air temperature, never below it
- Feeding Birds Cornell Lab of Ornithology, Project FeederWatch Mold and fungi in sugar water, and cleaning nectar feeders at every refill