You cannot beat the physics, but you can push the margin. Making snow in warm, marginal conditions comes down to four things: working the wet-bulb temperature rather than the air temperature, timing production to the coldest hours, optimising droplet size and nucleation, and — the newest lever — a polymer additive that widens the productive window by a modelled +3 °C. Only a refrigerated all-weather machine makes snow well above freezing.
Every snowmaking manager knows the frustration: the calendar says open, the forecast says +4 °C, and the guns are silent. This guide is the practical playbook for the marginal window — what "too warm" actually means, the levers that squeeze more usable hours out of a warm spell, and where the hard limit sits.
Key takeaways
- What matters is the wet-bulb temperature, not the air temperature — dry air lets you make snow above 0 °C air temperature.
- Conventional guns produce well down to about −2.5 °C wet-bulb and taper off above it; the exact ceiling depends on humidity, water temperature, and gun type.
- The operator levers for a warm spell are: chase the wet-bulb, time the cold hours, cool the water, tune droplet size, and dose an additive.
- A polymer additive (SL6733) targets a modelled +3 °C wet-bulb advantage — recovering marginal hours the guns would otherwise lose.
- Above the additive-extended window, only a refrigerated all-weather machine works, at far higher energy cost. SL6733 figures are modelled and pre-commercial.
Can you make snow above freezing?
Yes — often. Conventional snow guns regularly make snow when the air temperature is above 0 °C, because what governs droplet freezing is the wet-bulb temperature, which is lower than the air temperature whenever the air is dry. In low humidity you can make snow at +2 or +3 °C air temperature. What you cannot do with a gun is make snow when the wet-bulb itself is above roughly −2 °C, no matter how dry it gets.
The reason is evaporative cooling. As a water droplet flies through unsaturated air, some of it evaporates, and evaporation pulls heat out of what remains — cooling the droplet below the air temperature toward the wet-bulb temperature. Dry air is a powerful heat sink; humid air is not. This is why two resorts at the same +1 °C air temperature can have completely different snowmaking outcomes: the one at 30% humidity is making snow and the one at 90% humidity is not. The mechanism is explained in full in the wet-bulb temperature and snowmaking guide.
What temperature do you actually need?
You need a wet-bulb temperature of roughly −2.5 °C or colder for reliable conventional snowmaking, with the marginal window running from about −2 °C down. The colder the wet-bulb, the more snow per hour and the drier the snow. The table below maps the practical zones — but treat the boundaries as approximate, because water temperature, droplet size, and gun design all shift them.
| Wet-bulb temperature | Conventional gun result | Practical note | |---|---|---| | Above −1 °C | Effectively none | Guns off; only an all-weather machine works | | −1 to −2 °C | Marginal, wet, low yield | The window an additive targets | | −2.5 to −5 °C | Reliable, moderate yield | Standard early-season production | | −5 to −10 °C | Strong, drier snow | Efficient, high-yield production | | Below −10 °C | Maximum yield | Limited only by water supply and equipment |
The strategic point for a warming climate: the hours that used to sit at −5 °C increasingly sit at −1.5 °C. The total cold is shrinking, and what is left concentrates in the marginal band where guns are least productive. That is the exact band the newer levers are built to recover, and it is why marginal-window performance — not peak-cold performance — is the operator metric that now decides seasons. The economic stakes are laid out in the snowmaking cost per acre-foot breakdown.
How do operators squeeze the marginal window today?
By stacking the conventional levers: chase the wet-bulb around the clock, cool the feed water, tune droplet size, and start nucleation as early as possible. None of these makes snow above freezing on its own, but together they move the practical ceiling up by a degree or so and win the hours at the edge of the window.
The working checklist for a warm spell:
- Chase the wet-bulb, not the clock. The wet-bulb swings through the night and with weather fronts. Automated systems that start and stop guns on live wet-bulb readings capture short cold windows a manual crew would miss.
- Cool the feed water. Warmer water needs more evaporative cooling to freeze. Drawing from a cold reservoir bottom, or pre-cooling, meaningfully improves the marginal window.
- Tune droplet size. Smaller droplets have more surface area and shed heat faster, so they freeze in warmer conditions — at the cost of throw distance and yield. Marginal conditions call for a finer spray.
- Nucleate early. Getting ice crystals started (with a nucleant) raises the temperature at which droplets begin to freeze, so more of each droplet solidifies before it lands.
- Prioritise the cold nights. In a marginal week, disproportionate output comes from a few coldest hours — concentrate water and crews there rather than running thin all day.
These are the tools an experienced snowmaking team already uses. They are necessary but, in a warming climate, increasingly not sufficient — which is where chemistry comes in.
Can an additive make snow at warmer temperatures?
An additive does not make snow above freezing, but it does let conventional guns keep producing higher up the wet-bulb scale than they otherwise could — a modelled +3 °C advantage for a polymer like SL6733. It works on the water chemistry, not the machine: it raises the temperature at which droplets nucleate and freeze, and it inhibits the recrystallization that degrades marginal-condition snow.
DeepSnow's SL6733 combines an ultra-high-molecular-weight anionic poly(acrylamide-co-sodium acrylate) — an ice recrystallization inhibitor — with a cold-water-swelling starch nucleant, at a 6–7.6 ppm dose. The category and mechanism are explained in how polymer snowmaking additives work, and the competitive landscape against biological nucleants like Snomax is in the Snomax alternative analysis. The modelled +3 °C wet-bulb advantage means a gun that shuts off at −2 °C wet-bulb could keep producing usable snow toward +1 °C wet-bulb — turning lost hours into productive ones without touching the equipment.
The honest framing: this is a window extender, not a temperature eliminator. It stacks on top of the operator levers above; it does not replace them. And it is pre-commercial — EU lab pilots are targeted for the 2026/27 season — so the +3 °C figure is a modelled target to be confirmed in pilot. The product detail is in what is SL6733.
When do you need an all-weather machine instead?
When you need snow well above freezing — say +5 to +25 °C — no additive and no conventional gun will do it, and a refrigerated all-weather machine is the only option. These machines make cold internally instead of borrowing it from the air, so they are temperature-independent, but they use roughly 6–65 kWh per cubic metre, an order of magnitude or more above a conventional gun.
That energy penalty is why all-weather machines are point solutions — a snow guarantee for an event, a small beginner area, an indoor slope — rather than whole-mountain tools. TechnoAlpin's SnowFactory and the IDE All Weather Snowmaker both make snow at any temperature, but you would not refrigerate an entire ski area. The full cost comparison — additive versus machine — is in snowmaking additive vs all-weather machine. The practical hierarchy: conventional levers first, additive chemistry to extend the marginal window, all-weather machines only for the small patches that must have snow regardless of weather.
How much is the marginal window worth?
A great deal, because the marginal hours are exactly the ones that decide opening dates. A modelled 300–500 recovered snowmaking hours per season, from a +3 °C wider window, translates to roughly $2.4–2.8M of EBITDA uplift for a mid-sized Alpine resort — modelled, pre-commercial figures, but they reflect where the value sits: earlier, more reliable openings drive lift-ticket, lodging, and food-and-beverage revenue.
The point is not that warmer-temperature snowmaking is a nice-to-have. In a climate where the cold is shrinking and concentrating in the marginal band, the productive window at the edge is where seasons are won or lost. Every lever that moves the ceiling up — engineering or chemistry — is defending the revenue behind it, which is far larger than the cost of the lever.
The bottom line
"Too warm to make snow" almost always means "too warm for the guns as currently run," not "physically impossible." Work the wet-bulb, cool the water, tune the spray, and time the cold — and, where it is available, extend the window with additive chemistry. Reserve the energy-hungry all-weather machine for the small patches that truly need snow above freezing. The marginal window is manageable, and it is where the season is decided.
If you want to model how much of your lost marginal-hour production a wider window would recover, request a pilot or send us a message.
SL6733's +3 °C wet-bulb advantage, 300–500 recovered hours, and $2.4–2.8M EBITDA uplift are modelled and pre-commercial; EU lab pilots are targeted for the 2026/27 season. Wet-bulb thresholds are approximate and vary with humidity, water temperature, and equipment.