Bay St. Louis, Mississippi climate: Normal weather by month, frost dates and records
Bay St. Louis's normal year runs from 40°F January nights to 89°F July afternoons, with 64.0 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 18.7°C, January lows of 4°C, July highs of 32°C, 1,626 mm of precipitation a year.
- NOAA stationBay St Louis Nasa
- Station IDUSC00220521
- Location30.38°N 89.60°W
- Elevation30 ft (9 m)
- Population10,526
On October 14, the normal high in Bay St. Louis is 78°F and the normal low 57°F, and the chance of measurable rain or snow is 19%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Bay St. Louis.
- Jan 60° 40°
- Feb 64° 43°
- Mar 69° 48°
- Apr 75° 54°
- May 82° 62°
- Jun 87° 69°
- Jul 89° 71°
- Aug 89° 71°
- Sep 85° 67°
- Oct 78° 56°
- Nov 69° 45°
- Dec 61° 41°
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 Bay St. Louis each month?
July is the warmest month, with normal highs of 89°F; January the coldest, with normal lows of 40°F. The most precipitation falls in July (7.77 in), the least in February (4.10 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 60°F | 40°F | 49.7°F | 5.63 | 9 | <1 | 9 | 10 h 20 min |
| February | 64°F | 43°F | 53.0°F | 4.10 | 7 | <1 | 6 | 11 h 10 min |
| March | 69°F | 48°F | 58.5°F | 4.29 | 7 | <1 | 2 | 12 h |
| April | 75°F | 54°F | 64.4°F | 6.52 | 6 | <1 | <1 | 12 h 50 min |
| May | 82°F | 62°F | 71.8°F | 4.45 | 6 | 5 | <1 | 13 h 40 min |
| June | 87°F | 69°F | 77.9°F | 5.62 | 11 | 16 | <1 | 14 h 10 min |
| July | 89°F | 71°F | 80.1°F | 7.77 | 12 | 22 | <1 | 14 h |
| August | 89°F | 71°F | 79.9°F | 6.53 | 10 | 24 | <1 | 13 h 20 min |
| September | 85°F | 67°F | 75.9°F | 5.01 | 8 | 13 | <1 | 12 h 20 min |
| October | 78°F | 56°F | 67.1°F | 5.09 | 6 | 1 | <1 | 11 h 30 min |
| November | 69°F | 45°F | 57.1°F | 4.53 | 7 | <1 | 4 | 10 h 40 min |
| December | 61°F | 41°F | 51.3°F | 4.47 | 7 | <1 | 10 | 10 h 10 min |
| Year (annual) | 75°F | 56°F | 65.6°F | 64.01 | 95 | 80 | 31 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 15°C | 4°C | 9.8°C | 143 mm |
| February | 18°C | 6°C | 11.7°C | 104 mm |
| March | 20°C | 9°C | 14.7°C | 109 mm |
| April | 24°C | 12°C | 18.0°C | 166 mm |
| May | 28°C | 17°C | 22.1°C | 113 mm |
| June | 30°C | 21°C | 25.5°C | 143 mm |
| July | 32°C | 22°C | 26.7°C | 197 mm |
| August | 32°C | 22°C | 26.6°C | 166 mm |
| September | 29°C | 19°C | 24.4°C | 127 mm |
| October | 25°C | 14°C | 19.5°C | 129 mm |
| November | 21°C | 7°C | 13.9°C | 115 mm |
| December | 16°C | 5°C | 10.7°C | 114 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Slidell station (13 miles away), gets 0 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00220521; 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 Bay St. Louis?
Normal highs sit between 65°F and 85°F in March, April, May, September, October and November. Of those, October has the fewest days with rain (6).
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 USC00220521.
When is the last frost in Bay St. Louis?
In Bay St. Louis, the last spring frost (32°F) comes after March 6 in half of years and after March 27 in one year in ten; the first autumn frost comes before November 19 in half of years and before November 3 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
- March 61 year in 10 after March 27; 9 in 10 after February 5
- First autumn frost, half of years before
- November 191 year in 10 before November 3; 9 in 10 before December 13
NOAA puts the median frost-free season at 262 days, and the season without a hard freeze (28°F) at 296 days.
A hard freeze (28°F) comes after February 16 in half of springs and before December 4 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Bay St. Louis in zone 9a in ZIP code 39520.
Frost dates for every NOAA station in Mississippi · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00220521; 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 Bay St. Louis?
In a normal year in Bay St. Louis, 80 days a year reach 90°F (2 of them 100°F or more), 31 nights fall to 32°F or colder and 95 days bring measurable precipitation.
- Days at 90°F or more
- 80a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 31a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 95a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USC00220521.
How sunny is Bay St. Louis?
Over a year 79% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Bay St. Louis, 4.7 kWh per square metre a day. October is the sunniest month (84%) and February the cloudiest (71%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 73% | 3.0 |
| February | 71% | 3.5 |
| March | 76% | 4.7 |
| April | 80% | 5.8 |
| May | 83% | 6.4 |
| June | 80% | 6.2 |
| July | 78% | 5.9 |
| August | 80% | 5.6 |
| September | 83% | 5.2 |
| October | 84% | 4.5 |
| November | 81% | 3.5 |
| December | 72% | 2.7 |
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 Bay St. Louis need?
A normal year in Bay St. Louis brings 1,911 heating degree days, 64% fewer than the median U.S. place (5,373), and 2,140 cooling degree days, 2.4 times the median (908). Three months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 6,027 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 477 | 3 |
| February | 344 | 9 |
| March | 228 | 26 |
| April | 93 | 75 |
| May | 11 | 222 |
| June | 0 | 387 |
| July | 0 | 468 |
| August | 0 | 462 |
| September | 1 | 328 |
| October | 63 | 128 |
| November | 261 | 24 |
| December | 433 | 9 |
| Year (annual) | 1,911 | 2,140 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00220521. 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 Bay St. Louis's climate compare?
Bay St. Louis is warmer than 56 of the other 80 places with their own NOAA record in Mississippi, and wetter than 67. Across the 7,247 U.S. stations with normals, its annual mean of 65.6°F is warmer than 89%.
In the Köppen classification computed from these normals, Bay St. Louis 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 Bay St. Louis share this climate record?
2 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.
- Eden Isle, LA7,753 people · 16 mi SW
- Pearl River, LA2,647 people · 9 mi W
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 Bay St. Louis's climate
What is the coldest month in Bay St. Louis?
January, with a normal high of 60°F and a normal low of 40°F. The warmest is July (89°F by day, 71°F at night).
Does it snow in Bay St. Louis?
Rarely. NOAA publishes no 1991-2020 snowfall normal for Bay St. Louis's NOAA station; the nearest record that keeps one, Slidell station (13 miles away), records 0 inches of snow in a normal year.
What is the rainiest month in Bay St. Louis?
July, with 7.77 in of precipitation in a normal year; the driest is February with 4.10 in.
What plant hardiness zone is Bay St. Louis in?
The USDA's 2023 map puts Bay St. Louis in zone 9a in ZIP code 39520.
How late can frost come in Bay St. Louis?
In half of years the last 32°F night comes after March 6; in one year in ten it comes after March 27. Waiting until March 27 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Mississippi climateThe statewide normals and every place in the state
- Picayune, MS13 miles from this station, 66.4°F a year
- Slidell, LA14 miles from this station, 67.7°F a year
- Waveland, MS14 miles from this station, 67.0°F a year
- Gulfport, MS31 miles from this station, 68.3°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made