Alton, Missouri climate: Normal weather by month, frost dates and records
Alton's normal year runs from 22°F January nights to 88°F July afternoons, with 47.2 inches of precipitation and 4 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 13.2°C, January lows of −5°C, July highs of 31°C, 1,200 mm of precipitation a year.
- NOAA stationAlton
- Station IDUSC00230127
- Location36.69°N 91.40°W
- Elevation813 ft (248 m)
- From the centerunder 1 mile
- Population702
On October 23, the normal high in Alton is 68°F and the normal low 40°F, and the chance of measurable rain or snow is 23%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Alton.
- Jan 44° 22°
- Feb 49° 25°
- Mar 58° 34°
- Apr 69° 43°
- May 76° 53°
- Jun 85° 62°
- Jul 88° 66°
- Aug 88° 64°
- Sep 81° 55°
- Oct 70° 43°
- Nov 57° 33°
- Dec 46° 26°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Alton each month?
July is the warmest month, with normal highs of 88°F; January the coldest, with normal lows of 22°F. The most precipitation falls in May (5.57 in), the least in January (2.96 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 44°F | 22°F | 33.1°F | 2.96 | 1.7 | 6 | <1 | 26 | 9 h 50 min |
| February | 49°F | 25°F | 36.9°F | 3.39 | 0.8 | 7 | <1 | 21 | 10 h 50 min |
| March | 58°F | 34°F | 46.0°F | 4.45 | 0.9 | 9 | <1 | 15 | 11 h 50 min |
| April | 69°F | 43°F | 56.0°F | 4.66 | 0.0 | 8 | <1 | 5 | 13 h 10 min |
| May | 76°F | 53°F | 64.5°F | 5.57 | 0.0 | 10 | 1 | <1 | 14 h 10 min |
| June | 85°F | 62°F | 73.4°F | 3.31 | 0.0 | 7 | 9 | <1 | 14 h 40 min |
| July | 88°F | 66°F | 77.1°F | 4.01 | 0.0 | 7 | 17 | <1 | 14 h 30 min |
| August | 88°F | 64°F | 76.1°F | 3.92 | 0.0 | 7 | 16 | <1 | 13 h 40 min |
| September | 81°F | 55°F | 68.1°F | 3.46 | 0.0 | 5 | 5 | <1 | 12 h 30 min |
| October | 70°F | 43°F | 56.5°F | 3.77 | 0.0 | 6 | <1 | 5 | 11 h 20 min |
| November | 57°F | 33°F | 45.0°F | 4.44 | 0.0 | 7 | <1 | 14 | 10 h 10 min |
| December | 46°F | 26°F | 35.8°F | 3.29 | 0.8 | 7 | <1 | 24 | 9 h 40 min |
| Year (annual) | 68°F | 44°F | 55.7°F | 47.23 | 4.2 | 87 | 48 | 110 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 7°C | −5°C | 0.6°C | 75 mm | 4 cm |
| February | 9°C | −4°C | 2.7°C | 86 mm | 2 cm |
| March | 15°C | 1°C | 7.8°C | 113 mm | 2 cm |
| April | 20°C | 6°C | 13.3°C | 118 mm | 0 cm |
| May | 24°C | 12°C | 18.1°C | 141 mm | 0 cm |
| June | 29°C | 17°C | 23.0°C | 84 mm | 0 cm |
| July | 31°C | 19°C | 25.1°C | 102 mm | 0 cm |
| August | 31°C | 18°C | 24.5°C | 100 mm | 0 cm |
| September | 27°C | 13°C | 20.1°C | 88 mm | 0 cm |
| October | 21°C | 6°C | 13.6°C | 96 mm | 0 cm |
| November | 14°C | 1°C | 7.2°C | 113 mm | 0 cm |
| December | 8°C | −4°C | 2.1°C | 84 mm | 2 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00230127; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Alton?
Normal highs sit between 65°F and 85°F in April, May, June, September and October. Of those, September has the fewest days with rain (5).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00230127.
When is the last frost in Alton?
In Alton, the last spring frost (32°F) comes after April 17 in half of years and after May 1 in one year in ten; the first autumn frost comes before October 21 in half of years and before October 7 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 171 year in 10 after May 1; 9 in 10 after March 30
- First autumn frost, half of years before
- October 211 year in 10 before October 7; 9 in 10 before November 3
NOAA puts the median frost-free season at 187 days, and the season without a hard freeze (28°F) at 208 days.
A hard freeze (28°F) comes after April 5 in half of springs and before October 30 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Alton in zone 7a in ZIP code 65606, the nearest ZIP area.
Frost dates for every NOAA station in Missouri · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00230127; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Alton?
In a normal year in Alton, 48 days a year reach 90°F (3 of them 100°F or more), 110 nights fall to 32°F or colder and 87 days bring measurable precipitation.
- Days at 90°F or more
- 48a normal year
- Days at 100°F or more
- 3a normal year
- Nights at 32°F or colder
- 110a normal year
- Days that stay below freezing
- 13high of 32°F or less
- Days with 0.01 inch of precipitation
- 87a normal year
- Days with 1 inch of snow or more
- 2a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USC00230127.
How sunny is Alton?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Alton, 4.4 kWh per square metre a day. July is the sunniest month (82%) and February the cloudiest (67%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 70% | 2.4 |
| February | 67% | 3.0 |
| March | 70% | 4.1 |
| April | 73% | 5.2 |
| May | 74% | 5.8 |
| June | 82% | 6.7 |
| July | 82% | 6.4 |
| August | 82% | 5.7 |
| September | 81% | 4.9 |
| October | 76% | 3.6 |
| November | 74% | 2.7 |
| December | 68% | 2.1 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Alton need?
A normal year in Alton brings 4,622 heating degree days, 14% fewer than the median U.S. place (5,373), and 1,261 cooling degree days, 39% more than the median (908). Five months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,981 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 989 | 0 |
| February | 788 | 0 |
| March | 592 | 3 |
| April | 295 | 24 |
| May | 103 | 86 |
| June | 8 | 258 |
| July | 1 | 376 |
| August | 2 | 348 |
| September | 50 | 143 |
| October | 286 | 22 |
| November | 603 | 1 |
| December | 905 | 0 |
| Year (annual) | 4,622 | 1,261 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00230127. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Alton been warmer than normal lately?
2025 averaged 57.8°F, 2.1°F above the 1991-2020 normal of 55.7°F. 2 of the 2 complete years since 2024 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2024 | 59.2°F | +3.5°F | 57.46 | 3.4 |
| 2025 | 57.8°F | +2.1°F | 50.69 | – |
Source: observed years: ACIS, station USC00230127. A year counts only with all twelve months complete.
How does Alton's climate compare?
Alton is warmer than 78 of the other 133 places with their own NOAA record in Missouri, and wetter than 101. Across the 7,247 U.S. stations with normals, its annual mean of 55.7°F is warmer than 63%.
In the Köppen classification computed from these normals, Alton is Cfa: temperate, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Alton share this climate record?
Thomasville has no NOAA station with 1991-2020 normals of its own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Thomasville, MO35 people · 10 mi NW
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Alton's climate
What is the coldest month in Alton?
January, with a normal high of 44°F and a normal low of 22°F. The warmest is July (88°F by day, 66°F at night).
Does it snow in Alton?
Yes: 4 inches in a normal year, falling on 3 days with 0.1 inch or more, the most in January (1.7 inches).
What is the rainiest month in Alton?
May, with 5.57 in of precipitation in a normal year; the driest is January with 2.96 in.
What plant hardiness zone is Alton in?
The USDA's 2023 map puts Alton in zone 7a in ZIP code 65606, the nearest ZIP area.
How late can frost come in Alton?
In half of years the last 32°F night comes after April 17; in one year in ten it comes after May 1. Waiting until May 1 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Missouri climateThe statewide normals and every place in the state
- Mammoth Spring, AR16 miles from this station, 57.4°F a year
- Winona, MO20 miles from this station, 54.0°F a year
- Hardy, AR29 miles from this station, 58.4°F a year
- West Plains, MO30 miles from this station, 57.0°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made