Climate and average weather in Saint Peters
In Saint Peters, the summers are humid, hot, showery, and partly cloudy and the winters are cold, snowy, and partly cloudy.
Over the course of the year, the temperature in Saint Peters typically varies from 24°F to 87°F, and is rarely below 7°F or above 96°F. July is the hottest month of the year, while January is the coldest.
Based on the travel score, the best times of year to visit Saint Peters for warm-weather activities are from early May to late May and early September to late October.
- Hottest
- Jul
- 87°
- Coldest
- Jan
- 24°
- Wettest
- May
- 4.9 in
- Driest
- Feb
- 2.4 in
- Rain / yr
- 40.5 in
- 113 wet days
- Daylight
- 9.3–14.7 h
- shortest–longest
- Elevation
- 440 ft
- 38.8°N
- Clearest
- Sep
- 45% cloud
Saint Peters is city in Missouri.
- Density
- 908/km²
- people per km²
- Founded
- 1910
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Saint Peters weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around early September to late October.
Temperature through the year
Daily average highs and lows in Saint Peters, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 4.3 months, from May 19 to September 25, with daily high temperatures above 76°F. The hottest month of the year in Saint Peters is July, with an average high of 87°F and low of 70°F.
The cool season lasts 3.0 months, from November 30 to February 27, with daily high temperatures below 49°F. The coldest month of the year in Saint Peters is January, with an average low of 24°F and high of 40°F.
Days typically run about 18°F warmer than nights year-round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 40 | 44 | 55 | 66 | 75 | 84 | 87 | 86 | 79 | 67 | 54 | 43 |
| Avg low (°F) | 24 | 28 | 37 | 47 | 57 | 66 | 70 | 67 | 59 | 48 | 37 | 28 |
| Avg high (°F) | Avg low (°F) | |
|---|---|---|
| Jan | 40 | 24 |
| Feb | 44 | 28 |
| Mar | 55 | 37 |
| Apr | 66 | 47 |
| May | 75 | 57 |
| Jun | 84 | 66 |
| Jul | 87 | 70 |
| Aug | 86 | 67 |
| Sep | 79 | 59 |
| Oct | 67 | 48 |
| Nov | 54 | 37 |
| Dec | 43 | 28 |
How hot and cold Saint Peters really feels
The felt-temperature range through the year — heat index on the day's high (summer humidity), wind chill on the night's low (winter wind). The dashed lines are the plain thermometer; the gap is how much hotter or colder it really feels.
On the hottest afternoons, once humidity is folded in, Saint Peters feels like about 92°F (around July 15). About 27 days a year carry some heat stress, peaking in July.
On the coldest nights, wind chill pulls the feels-like down to about 15°F (around January 16), with roughly 124 freezing days a year (feels-like at or below 32°F), worst in January.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°F) | 40 | 44 | 55 | 66 | 75 | 85 | 91 | 88 | 79 | 67 | 54 | 43 |
| Air high (°F) | 40 | 44 | 55 | 66 | 75 | 84 | 87 | 86 | 79 | 67 | 54 | 43 |
| Feels-like low (°F) | 16 | 20 | 31 | 44 | 57 | 66 | 70 | 68 | 59 | 45 | 31 | 21 |
| Air low (°F) | 24 | 28 | 37 | 47 | 57 | 66 | 70 | 67 | 59 | 48 | 37 | 28 |
| Feels-like high (°F) | Air high (°F) | Feels-like low (°F) | Air low (°F) | |
|---|---|---|---|---|
| Jan | 40 | 40 | 16 | 24 |
| Feb | 44 | 44 | 20 | 28 |
| Mar | 55 | 55 | 31 | 37 |
| Apr | 66 | 66 | 44 | 47 |
| May | 75 | 75 | 57 | 57 |
| Jun | 85 | 84 | 66 | 66 |
| Jul | 91 | 87 | 70 | 70 |
| Aug | 88 | 86 | 68 | 67 |
| Sep | 79 | 79 | 59 | 59 |
| Oct | 67 | 67 | 45 | 48 |
| Nov | 54 | 54 | 31 | 37 |
| Dec | 43 | 43 | 21 | 28 |
Average hourly temperature in Saint Peters
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on July afternoons, near 87°F, and coldest before dawn in January, near 24°F.
Saint Peters weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 40° / 24° | 2.5 | 7.7 | 3 | 9.6 | 0.0 |
| Feb | 44° / 28° | 2.4 | 7.6 | 2.9 | 10.5 | 0.8 |
| Mar | 55° / 37° | 3.6 | 10.6 | 1.4 | 11.7 | 3.5 |
| Apr | 66° / 47° | 4.5 | 11.3 | 0.2 | 13 | 5.8 |
| May | 75° / 57° | 4.9 | 13.3 | 0 | 14.1 | 6.3 |
| Jun | 84° / 66° | 4.0 | 11.1 | 0 | 14.7 | 5.5 |
| Jul | 87° / 70° | 3.2 | 9.9 | 0 | 14.4 | 4.6 |
| Aug | 86° / 67° | 3.0 | 9.2 | 0 | 13.5 | 5.2 |
| Sep | 79° / 59° | 3.2 | 7.6 | 0 | 12.3 | 7.1 |
| Oct | 67° / 48° | 3.3 | 8.5 | 0 | 11 | 6.6 |
| Nov | 54° / 37° | 3.5 | 8.3 | 0.8 | 9.9 | 3.5 |
| Dec | 43° / 28° | 2.4 | 7.7 | 2.2 | 9.3 | 0.6 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Saint Peters gets about 40.5 in of precipitation a year. On a typical day the chance of rain is often wet, but that rises and falls sharply with the seasons.
The wetter season lasts 4.6 months, from around Feb 24 to Jul 13, peaking in April at about 44% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Jan 30.
May is the wettest month by volume, with 4.9 in over about 13 wet days; February is the driest, with 2.4 in. Some of the cold-season precipitation falls as snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 25 | 27 | 34 | 38 | 42 | 38 | 32 | 29 | 26 | 27 | 28 | 26 |
| Rain days | 8 | 8 | 11 | 11 | 13 | 11 | 10 | 9 | 8 | 9 | 8 | 8 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 25 | 8 |
| Feb | 27 | 8 |
| Mar | 34 | 11 |
| Apr | 38 | 11 |
| May | 42 | 13 |
| Jun | 38 | 11 |
| Jul | 32 | 10 |
| Aug | 29 | 9 |
| Sep | 26 | 8 |
| Oct | 27 | 9 |
| Nov | 28 | 8 |
| Dec | 26 | 8 |
Monthly rainfall
Over a full year, Saint Peters collects about 40.5 in of rain across 113 wet days — roughly 3.4 in in an average month.
It doesn’t fall evenly. May is the wettest month with 4.9 in, while February is the driest at just 2.4 in. The three wettest months alone bring about 33% of the year’s total, and some of the cold-season precipitation falls as snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (in) | 2.5 | 2.4 | 3.6 | 4.5 | 4.9 | 4.0 | 3.2 | 3.0 | 3.2 | 3.3 | 3.5 | 2.4 |
| Rain days | 8 | 8 | 11 | 11 | 13 | 11 | 10 | 9 | 8 | 9 | 8 | 8 |
| Snow days | 3 | 3 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 2 |
| Rainfall (in) | Rain days | Snow days | |
|---|---|---|---|
| Jan | 2.5 | 8 | 3 |
| Feb | 2.4 | 8 | 3 |
| Mar | 3.6 | 11 | 1 |
| Apr | 4.5 | 11 | 0 |
| May | 4.9 | 13 | 0 |
| Jun | 4.0 | 11 | 0 |
| Jul | 3.2 | 10 | 0 |
| Aug | 3.0 | 9 | 0 |
| Sep | 3.2 | 8 | 0 |
| Oct | 3.3 | 9 | 0 |
| Nov | 3.5 | 8 | 1 |
| Dec | 2.4 | 8 | 2 |
Snow in Saint Peters
Average snowy days through the year, the snow-season span, and estimated snowfall — for ski trips and the perennial 'will there be snow at Christmas?' question.
Saint Peters averages about 11 snowy days a year. Snow season runs roughly Nov 4 to Apr 4 — about 5 months.
January is snowiest, with roughly 3 days of snow and an estimated 6 in of snowfall. Over the year that adds up to an estimated 21 in of snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Snow days | 3 | 3 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 2 |
| Snowfall (in) | 6 | 6 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 4 |
| Snow days | Snowfall (in) | |
|---|---|---|
| Jan | 3 | 6 |
| Feb | 3 | 6 |
| Mar | 1 | 3 |
| Apr | 0 | 0 |
| May | 0 | 0 |
| Jun | 0 | 0 |
| Jul | 0 | 0 |
| Aug | 0 | 0 |
| Sep | 0 | 0 |
| Oct | 0 | 0 |
| Nov | 1 | 1 |
| Dec | 2 | 4 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Saint Peters, the average share of the sky covered by clouds shows moderate seasonal variation over the course of the year.
The clearer part of the year begins around June 9 and lasts for 4.8 months, ending around October 31. The clearest month is September, when the sky is clear, mostly clear, or partly cloudy 63% of the time on average.
The cloudier part of the year begins around November 23 and lasts for 6.5 months, ending around June 8. The cloudiest month is February, when it is overcast or mostly cloudy 61% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 41 | 39 | 41 | 45 | 43 | 52 | 58 | 62 | 63 | 57 | 49 | 42 |
| Cloudier (%) | 59 | 61 | 59 | 55 | 57 | 48 | 42 | 38 | 37 | 43 | 51 | 58 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 41 | 59 |
| Feb | 39 | 61 |
| Mar | 41 | 59 |
| Apr | 45 | 55 |
| May | 43 | 57 |
| Jun | 52 | 48 |
| Jul | 58 | 42 |
| Aug | 62 | 38 |
| Sep | 63 | 37 |
| Oct | 57 | 43 |
| Nov | 49 | 51 |
| Dec | 42 | 58 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around June 11, brings about 14 h 42 min of light; the shortest, around January 1, only 9 h 18 min — a swing of roughly 5 h 24 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 9.6 | 10.5 | 11.7 | 13.0 | 14.1 | 14.7 | 14.4 | 13.5 | 12.3 | 11.0 | 9.9 | 9.3 |
| Sunrise (AM) | 7:25 | 7:02 | 6:22 | 5:32 | 4:55 | 4:42 | 4:54 | 5:21 | 5:49 | 6:18 | 6:52 | 7:20 |
| Sunset (PM) | 4:59 | 5:32 | 6:03 | 6:33 | 7:02 | 7:24 | 7:22 | 6:52 | 6:04 | 5:17 | 4:43 | 4:38 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 9.6 | 7:25 | 4:59 |
| Feb | 10.5 | 7:02 | 5:32 |
| Mar | 11.7 | 6:22 | 6:03 |
| Apr | 13.0 | 5:32 | 6:33 |
| May | 14.1 | 4:55 | 7:02 |
| Jun | 14.7 | 4:42 | 7:24 |
| Jul | 14.4 | 4:54 | 7:22 |
| Aug | 13.5 | 5:21 | 6:52 |
| Sep | 12.3 | 5:49 | 6:04 |
| Oct | 11.0 | 6:18 | 5:17 |
| Nov | 9.9 | 6:52 | 4:43 |
| Dec | 9.3 | 7:20 | 4:38 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Saint Peters averages about 11 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 8 and 16 days.
The sunnier stretch runs 5.4 months, from around Jun 15 to Nov 25. The sunniest month is September, with roughly 15 sunny days (mixed).
The greyest month is February, down near 8 sunny days — about 44% fewer than the September peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 9 | 8 | 9 | 9 | 9 | 10 | 12 | 13 | 15 | 14 | 11 | 9 |
| Sky | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed |
| Sunny days | Sky | |
|---|---|---|
| Jan | 9 | Mixed |
| Feb | 8 | Mixed |
| Mar | 9 | Mixed |
| Apr | 9 | Mixed |
| May | 9 | Mixed |
| Jun | 10 | Mixed |
| Jul | 12 | Mixed |
| Aug | 13 | Mixed |
| Sep | 15 | Mixed |
| Oct | 14 | Mixed |
| Nov | 11 | Mixed |
| Dec | 9 | Mixed |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
In Saint Peters, how humid it feels changes dramatically over the year.
The more humid part of the year lasts 4.5 months, from around May 12 to September 25. The muggiest month is July, when the air feels humid, muggy or worse about 87% of the time.
The most comfortable stretch runs from around September 26 to May 11, and January is the most comfortable month — the air is dry or comfortable 100% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 100 | 99 | 96 | 83 | 48 | 12 | 2 | 5 | 35 | 79 | 95 | 99 |
| Comfortable (%) | 0 | 1 | 3 | 12 | 17 | 15 | 11 | 14 | 19 | 11 | 4 | 1 |
| Humid (%) | 0 | 0 | 1 | 5 | 18 | 21 | 20 | 21 | 20 | 8 | 1 | 0 |
| Muggy (%) | 0 | 0 | 0 | 0 | 16 | 34 | 29 | 32 | 19 | 3 | 0 | 0 |
| Oppressive (%) | 0 | 0 | 0 | 0 | 1 | 18 | 36 | 27 | 7 | 0 | 0 | 0 |
| Miserable (%) | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 1 | 0 | 0 | 0 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|---|---|
| Jan | 100 | 0 | 0 | 0 | 0 | 0 |
| Feb | 99 | 1 | 0 | 0 | 0 | 0 |
| Mar | 96 | 3 | 1 | 0 | 0 | 0 |
| Apr | 83 | 12 | 5 | 0 | 0 | 0 |
| May | 48 | 17 | 18 | 16 | 1 | 0 |
| Jun | 12 | 15 | 21 | 34 | 18 | 0 |
| Jul | 2 | 11 | 20 | 29 | 36 | 2 |
| Aug | 5 | 14 | 21 | 32 | 27 | 1 |
| Sep | 35 | 19 | 20 | 19 | 7 | 0 |
| Oct | 79 | 11 | 8 | 3 | 0 | 0 |
| Nov | 95 | 4 | 1 | 0 | 0 | 0 |
| Dec | 99 | 1 | 0 | 0 | 0 | 0 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in Saint Peters is typically calm, near 7 mph, and varies little with the seasons.
The windier part of the year lasts 7.1 months, from around Oct 11 to May 15. The windiest month is April, averaging about 8 mph (light breeze).
The calmer part of the year runs from around May 16 to Oct 10, with August the calmest month at about 5 mph.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (mph) | 7 | 7 | 8 | 8 | 7 | 6 | 5 | 5 | 6 | 7 | 7 | 7 |
| Feels | calm | calm | light breeze | light breeze | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (mph) | Feels | |
|---|---|---|
| Jan | 7 | calm |
| Feb | 7 | calm |
| Mar | 8 | light breeze |
| Apr | 8 | light breeze |
| May | 7 | calm |
| Jun | 6 | calm |
| Jul | 5 | calm |
| Aug | 5 | calm |
| Sep | 6 | calm |
| Oct | 7 | calm |
| Nov | 7 | calm |
| Dec | 7 | calm |
Best time to visit Saint Peters
To characterize how pleasant the weather is in Saint Peters throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around mid September, Saint Peters is still near the start of its best-weather window — great conditions with the peak-season crowds not yet at full swing.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 64°F and 82°F. Based on this score, the best times of year to visit Saint Peters for general outdoor tourist activities run from early May to early June and again from early September to late October, with a peak score in the last week of September.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 0.0 | 0.9 | 3.5 | 5.8 | 6.3 | 5.5 | 4.7 | 5.2 | 7.0 | 6.5 | 3.5 | 0.7 |
| Rating | poor | poor | fair | good | good | fair | fair | fair | good | good | poor | poor |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 0.0 | poor |
| Feb | 0.9 | poor |
| Mar | 3.5 | fair |
| Apr | 5.8 | good |
| May | 6.3 | good |
| Jun | 5.5 | fair |
| Jul | 4.7 | fair |
| Aug | 5.2 | fair |
| Sep | 7.0 | good |
| Oct | 6.5 | good |
| Nov | 3.5 | poor |
| Dec | 0.7 | poor |
The beach/pool score favors clear, rainless days with daytime highs between 75°F and 93°F. Based on this score, the best time of year to visit Saint Peters for hot-weather activities is from late May to early October, with a peak score in the first week of September.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for Saint Peters, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
For a warm-season trip around July (highs near 87°F), the essentials are light clothes, rain gear and sun protection. In the cold season around January (highs near 40°F), pack a warm layer and a heavy coat.
In July, Saint Peters sees daytime highs around 87°F and nights near 70°F. Pack light clothes and sun protection. Worth having: rain gear. About 10 days see rain.
UV index (midday) in Saint Peters by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
Under clear skies, the midday UV index in Saint Peters peaks around June 22 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 at about 2 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 3 | 5 | 7 | 8 | 9 | 9 | 8 | 7 | 4 | 3 | 2 |
| Level | Low | Moderate | Moderate | High | Very high | Very high | Very high | Very high | High | Moderate | Moderate | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Low |
| Feb | 3 | Moderate |
| Mar | 5 | Moderate |
| Apr | 7 | High |
| May | 8 | Very high |
| Jun | 9 | Very high |
| Jul | 9 | Very high |
| Aug | 8 | Very high |
| Sep | 7 | High |
| Oct | 4 | Moderate |
| Nov | 3 | Moderate |
| Dec | 2 | Low |
Average hourly UV index in Saint Peters
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in June the burn window is concentrated in the middle of the day: about 8.5 hours a day reach index 3 (protection recommended), and 5.5 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 0 | 2 | 5 | 6.5 | 8 | 8.5 | 8 | 7.5 | 6.5 | 4 | 1 | 0 |
| UV ≥ 6 (h/day) | 0 | 0 | 0 | 3 | 4.5 | 5.5 | 5.5 | 4.5 | 2.5 | 0 | 0 | 0 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 0 | 0 |
| Feb | 2 | 0 |
| Mar | 5 | 0 |
| Apr | 6.5 | 3 |
| May | 8 | 4.5 |
| Jun | 8.5 | 5.5 |
| Jul | 8 | 5.5 |
| Aug | 7.5 | 4.5 |
| Sep | 6.5 | 2.5 |
| Oct | 4 | 0 |
| Nov | 1 | 0 |
| Dec | 0 | 0 |
Air quality in Saint Peters by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly average.
Air quality in Saint Peters is worst in July — around 17 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (October, 7 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 9 | 11 | 11 | 10 | 13 | 14 | 17 | 14 | 11 | 7 | 7 | 8 |
| Level | Good | Good | Good | Good | Moderate | Moderate | Moderate | Moderate | Good | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 9 | Good |
| Feb | 11 | Good |
| Mar | 11 | Good |
| Apr | 10 | Good |
| May | 13 | Moderate |
| Jun | 14 | Moderate |
| Jul | 17 | Moderate |
| Aug | 14 | Moderate |
| Sep | 11 | Good |
| Oct | 7 | Good |
| Nov | 7 | Good |
| Dec | 8 | Good |
Growing season
The growing season in Saint Peters typically lasts about 272 days, from around March 5 to December 1 — the span where a frost-free day is more likely than not. It is reliably frost-free from April 9 to October 26.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 24 | 33 | 68 | 94 | 100 | 100 | 100 | 100 | 100 | 95 | 70 | 37 |
| Frost nights | 31 | 28 | 31 | 5 | 0 | 0 | 0 | 0 | 0 | 2 | 30 | 31 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 24 | 31 |
| Feb | 33 | 28 |
| Mar | 68 | 31 |
| Apr | 94 | 5 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 95 | 2 |
| Nov | 70 | 30 |
| Dec | 37 | 31 |
Growing degree days
Growing degree days tally heat above 50°F: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. Saint Peters banks about 3,987 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around July.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°F·days) | 0 | 0 | 4 | 195 | 499 | 753 | 891 | 829 | 577 | 236 | 2 | 0 |
| Growing degree days (°F·days) | |
|---|---|
| Jan | 0 |
| Feb | 0 |
| Mar | 4 |
| Apr | 195 |
| May | 499 |
| Jun | 753 |
| Jul | 891 |
| Aug | 829 |
| Sep | 577 |
| Oct | 236 |
| Nov | 2 |
| Dec | 0 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
Saint Peters receives about 4.3 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 1.9 and 6.6 kWh/m².
The brighter stretch of the year lasts 6.2 months, from around Mar 23 to Sep 28. The brightest month is June, averaging about 6.4 kWh/m² (intense).
The dimmest month is December, down near 1.9 kWh/m² — roughly 70% less than the June peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 2.2 | 3.1 | 4.1 | 5.2 | 5.8 | 6.4 | 6.4 | 5.8 | 4.8 | 3.5 | 2.4 | 1.9 |
| Level | Moderate | Moderate | Bright | Bright | Bright | Intense | Intense | Bright | Bright | Moderate | Moderate | Dim |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 2.2 | Moderate |
| Feb | 3.1 | Moderate |
| Mar | 4.1 | Bright |
| Apr | 5.2 | Bright |
| May | 5.8 | Bright |
| Jun | 6.4 | Intense |
| Jul | 6.4 | Intense |
| Aug | 5.8 | Bright |
| Sep | 4.8 | Bright |
| Oct | 3.5 | Moderate |
| Nov | 2.4 | Moderate |
| Dec | 1.9 | Dim |
Where is Saint Peters?
Saint Peters sits at 38.8°N, 90.6°W, 440 ft above sea level, in United States. The nearest listed city is O'Fallon, 3.7 mi away.
Topography around Saint Peters
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Saint Peters.
Within 2 miles, the terrain around Saint Peters has only modest variations in elevation — a maximum elevation change of 167 ft around an average of 469 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 469 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 978 ft.
The land around Saint Peters is covered by artificial surfaces (32%), trees (26%) and cropland (26%) within 2 miles, trees (36%) and cropland (27%) within 10 miles, and trees (51%) and cropland (32%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Saint Peters (38.8003°, -90.6265°, elevation 440 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).