St. Peters, Missouri climate: Normal weather by month, frost dates and records
St. Peters's normal year runs from 21°F January nights to 88°F July afternoons, with 42.3 inches of precipitation and 15 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 12.9°C, January lows of −6°C, July highs of 31°C, 1,075 mm of precipitation a year.
- NOAA stationSt Peters (2 mi SE)
- Station IDUSC00237475
- Location38.77°N 90.59°W
- Elevation575 ft (175 m)
- From the center1 miles
- Population61,398
On October 23, the normal high in St. Peters is 66°F and the normal low 43°F, and the chance of measurable rain or snow is 27%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for St. Peters.
- Jan 39° 21°
- Feb 45° 25°
- Mar 56° 33°
- Apr 67° 43°
- May 76° 54°
- Jun 84° 63°
- Jul 88° 68°
- Aug 87° 65°
- Sep 81° 57°
- Oct 69° 45°
- Nov 55° 35°
- Dec 44° 27°
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 St. Peters each month?
July is the warmest month, with normal highs of 88°F; January the coldest, with normal lows of 21°F. The most precipitation falls in May (4.80 in), the least in February (2.37 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 39°F | 21°F | 30.2°F | 2.44 | 4.7 | 8 | <1 | 26 | 9 h 40 min |
| February | 45°F | 25°F | 34.8°F | 2.37 | 5.0 | 8 | <1 | 23 | 10 h 40 min |
| March | 56°F | 33°F | 44.4°F | 3.46 | 1.5 | 11 | <1 | 15 | 11 h 50 min |
| April | 67°F | 43°F | 55.3°F | 4.74 | 0.1 | 11 | <1 | 3 | 13 h 10 min |
| May | 76°F | 54°F | 64.9°F | 4.80 | 0.0 | 13 | 2 | <1 | 14 h 20 min |
| June | 84°F | 63°F | 73.9°F | 4.26 | 0.0 | 10 | 9 | <1 | 14 h 50 min |
| July | 88°F | 68°F | 77.8°F | 4.23 | 0.0 | 9 | 13 | <1 | 14 h 40 min |
| August | 87°F | 65°F | 76.3°F | 3.76 | 0.0 | 8 | 11 | <1 | 13 h 40 min |
| September | 81°F | 57°F | 68.9°F | 3.07 | 0.0 | 8 | 4 | <1 | 12 h 30 min |
| October | 69°F | 45°F | 56.9°F | 3.11 | 0.0 | 8 | <1 | 2 | 11 h 20 min |
| November | 55°F | 35°F | 44.9°F | 3.54 | 0.8 | 9 | <1 | 12 | 10 h 10 min |
| December | 44°F | 27°F | 35.0°F | 2.56 | 2.7 | 9 | <1 | 22 | 9 h 30 min |
| Year (annual) | 66°F | 45°F | 55.3°F | 42.34 | 14.8 | 111 | 39 | 103 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 4°C | −6°C | −1.0°C | 62 mm | 12 cm |
| February | 7°C | −4°C | 1.6°C | 60 mm | 13 cm |
| March | 13°C | 1°C | 6.9°C | 88 mm | 4 cm |
| April | 20°C | 6°C | 12.9°C | 120 mm | 0 cm |
| May | 25°C | 12°C | 18.3°C | 122 mm | 0 cm |
| June | 29°C | 17°C | 23.3°C | 108 mm | 0 cm |
| July | 31°C | 20°C | 25.4°C | 107 mm | 0 cm |
| August | 31°C | 19°C | 24.6°C | 96 mm | 0 cm |
| September | 27°C | 14°C | 20.5°C | 78 mm | 0 cm |
| October | 20°C | 7°C | 13.8°C | 79 mm | 0 cm |
| November | 13°C | 2°C | 7.2°C | 90 mm | 2 cm |
| December | 6°C | −3°C | 1.7°C | 65 mm | 7 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00237475; 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 St. Peters?
Normal highs sit between 65°F and 85°F in April, May, June, September and October. Of those, October has the fewest days with rain (8).
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 USC00237475.
When is the last frost in St. Peters?
In St. Peters, the last spring frost (32°F) comes after April 9 in half of years and after April 25 in one year in ten; the first autumn frost comes before October 26 in half of years and before October 14 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 91 year in 10 after April 25; 9 in 10 after March 27
- First autumn frost, half of years before
- October 261 year in 10 before October 14; 9 in 10 before November 7
NOAA puts the median frost-free season at 198 days, and the season without a hard freeze (28°F) at 221 days.
A hard freeze (28°F) comes after March 31 in half of springs and before November 5 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts St. Peters in zone 6b in ZIP code 63376. By the map's own method, the average of each year's coldest night over 1991-2020, St. Peters's NOAA station is in zone 7a: the coldest night of a typical year reaches 1°F (15 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in Missouri · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00237475; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. 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 St. Peters?
In a normal year in St. Peters, 39 days a year reach 90°F (2 of them 100°F or more), 103 nights fall to 32°F or colder and 111 days bring measurable precipitation.
- Days at 90°F or more
- 39a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 103a normal year
- Days that stay below freezing
- 22high of 32°F or less
- Days with 0.01 inch of precipitation
- 111a normal year
- Days with 1 inch of snow or more
- 5a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USC00237475.
How sunny is St. Peters?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around St. Peters, 4.2 kWh per square metre a day. July is the sunniest month (82%) and December the cloudiest (66%). Among the 459 U.S. places of 50,000 or more, that ranks tied 304th (with 25 others) in sunshine.
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 67% | 2.1 |
| February | 66% | 2.8 |
| March | 67% | 3.8 |
| April | 73% | 5.0 |
| May | 74% | 5.6 |
| June | 81% | 6.4 |
| July | 82% | 6.3 |
| August | 81% | 5.6 |
| September | 81% | 4.8 |
| October | 76% | 3.4 |
| November | 72% | 2.4 |
| December | 66% | 1.8 |
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 St. Peters need?
A normal year in St. Peters brings 4,863 heating degree days, 9% fewer than the median U.S. place (5,373), and 1,357 cooling degree days, 50% more than the median (908). Six months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 4,056 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,077 | 0 |
| February | 844 | 0 |
| March | 644 | 6 |
| April | 315 | 24 |
| May | 109 | 106 |
| June | 9 | 274 |
| July | 1 | 397 |
| August | 3 | 353 |
| September | 49 | 167 |
| October | 279 | 26 |
| November | 604 | 3 |
| December | 928 | 0 |
| Year (annual) | 4,863 | 1,357 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00237475. 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.
How does St. Peters's climate compare?
St. Peters is warmer than 67 of the other 133 places with their own NOAA record in Missouri, and wetter than 48. Across the 7,247 U.S. stations with normals, its annual mean of 55.3°F is warmer than 61%.
In the Köppen classification computed from these normals, St. Peters is Dfa: continental, 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 St. Peters share this climate record?
4 places have no NOAA station with 1991-2020 normals of their 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.
- Cottleville, MO6,378 people · 4 mi W
- St. Paul, MO3,725 people · 10 mi NW
- Old Monroe, MO279 people · 14 mi NW
- Chain of Rocks, MO102 people · 15 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 St. Peters's climate
What is the coldest month in St. Peters?
January, with a normal high of 39°F and a normal low of 21°F. The warmest is July (88°F by day, 68°F at night).
Does it snow in St. Peters?
Yes: 15 inches in a normal year, falling on 10 days with 0.1 inch or more, the most in February (5.0 inches).
What is the rainiest month in St. Peters?
May, with 4.80 in of precipitation in a normal year; the driest is February with 2.37 in.
What plant hardiness zone is St. Peters in?
The USDA's 2023 map puts St. Peters in zone 6b in ZIP code 63376. By the same method at St. Peters's NOAA station, the coldest night of a typical year reaches 1°F (15 years, 1991-2020): zone 7a.
How late can frost come in St. Peters?
In half of years the last 32°F night comes after April 9; in one year in ten it comes after April 25. Waiting until April 25 leaves about a one-in-ten chance of a later frost.
Nearby and next
- St. Peters in OctoberThis month day by day, its records and recent years
- Missouri climateThe statewide normals and every place in the state
- Weldon Spring, MO7 miles from this station, 55.2°F a year
- St Louis Spirit of St. Louis Airport, MO9 miles from this station, 56.1°F a year
- St. Louis, MO12 miles from this station, 57.4°F a year
- St. Charles, MO14 miles from this station, 56.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made