Bethlehem, Pennsylvania climate: NOAA's gridded normals for the city, beside the nearest station records
NOAA's gridded 1991-2020 normals put Bethlehem's center at January lows of 20°F and July highs of 86°F, a yearly mean of 52.0°F and 48.2 inches of precipitation. No NOAA station keeps a record under the city's name. The nearest station record, Phillipsburg (10 miles NE, 232 ft), has January lows of 22°F and July highs of 86°F.
79,453 people (Census Bureau 2024). Distances and directions are from the city's center.
- Jan 38° 20°
- Feb 42° 22°
- Mar 50° 29°
- Apr 63° 38°
- May 73° 49°
- Jun 81° 58°
- Jul 86° 63°
- Aug 84° 61°
- Sep 77° 54°
- Oct 65° 42°
- Nov 54° 33°
- Dec 43° 26°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
The months above are NOAA's gridded normals at Bethlehem's center.
What is each month like in Bethlehem?
NOAA's grid estimates the normals every 5 km or so from the stations around each point, terrain included. It smooths between stations, so night lows at the heart of a large city can run warmer than the grid shows: at five big-city airports we compared, the grid's highs were within about 1°F of the station and its lows 1-6°F cooler. The nearest record's high and low are beside each month.
| Month | High | Low | Mean | Precip. | Phillipsburg high | Phillipsburg low |
|---|---|---|---|---|---|---|
| January | 38°F | 20°F | 29.2°F | 3.41 | 38°F | 22°F |
| February | 42°F | 22°F | 31.7°F | 2.71 | 40°F | 22°F |
| March | 50°F | 29°F | 39.6°F | 3.75 | 49°F | 29°F |
| April | 63°F | 38°F | 50.7°F | 3.84 | 62°F | 39°F |
| May | 73°F | 49°F | 60.9°F | 3.93 | 72°F | 49°F |
| June | 81°F | 58°F | 69.5°F | 4.41 | 81°F | 59°F |
| July | 86°F | 63°F | 74.5°F | 4.98 | 86°F | 64°F |
| August | 84°F | 61°F | 72.4°F | 4.71 | 83°F | 62°F |
| September | 77°F | 54°F | 65.3°F | 4.71 | 77°F | 55°F |
| October | 65°F | 42°F | 53.5°F | 4.38 | 65°F | 44°F |
| November | 54°F | 33°F | 43.1°F | 3.30 | 53°F | 33°F |
| December | 43°F | 26°F | 34.3°F | 4.00 | 43°F | 26°F |
In metric: a yearly mean of 11.1°C, January lows of −7°C, July highs of 30°C and 1,223 mm of precipitation a year.
Source: NOAA NCEI U.S. Monthly Gridded Climate Normals 1991-2020 (nClimGrid, accession 0245564); NOAA NCEI 1991-2020 station normals. The grid cell holding the city's Census center point.
What do the station records around Bethlehem say?
Each row is a NOAA station's own 1991-2020 normals, with the snow and frost dates the grid does not give. A record downhill or nearer the coast than the city can run warmer, one uphill cooler: compare the elevations.
| Record | Where | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| PhillipsburgPhillipsburg-Easton Bridge | 10 mi NE | 232 ft | 52.1°F | 22°F | 86°F | 51.0 | – | April 18 |
| AllentownAllentown Lehigh Valley International Airport | 5 mi W | 390 ft | 53.1°F | 22°F | 86°F | 47.4 | 33 | April 20 |
| Springtown (1 mi NNE) | 6 mi SE | 860 ft | 50.9°F | 19°F | 83°F | 53.4 | 41 | April 21 |
Source: NOAA NCEI 1991-2020 U.S. Climate Normals; place center and population: Census Bureau 2024. Last frost: the median last spring date of 32°F.
How much snow, how late a frost, what zone and how much sun in Bethlehem?
NOAA's grid gives no snow, frost dates or records, so these come from the nearest station record, Phillipsburg (10 miles NE, 232 ft). NOAA publishes no snowfall normal for it; the nearest record that has one, Allentown (5 miles W), gets 33 inches a year. The last spring frost (32°F) comes after April 18 in half of years and the first autumn frost before October 25.
The USDA's 2023 Plant Hardiness Zone Map puts Bethlehem in zone 7a across its 3 ZIP code areas.
Over a year 72% of the sunlight that would reach the ground under clear skies gets through the clouds in the area (3.9 kWh per square metre a day, NASA POWER 2001-2020); July is the sunniest month (79%) and December the cloudiest (63%).
Phillipsburg's page has its months, frost probabilities, records by month and recent years. NOAA's grid has monthly figures only, so there are no day-by-day month pages for Bethlehem; the nearest record's month pages have them.
Source: NOAA NCEI 1991-2020 normals, station USC00286979; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; sunshine: NASA POWER.
How does the climate vary across Bethlehem, ZIP code by ZIP code?
3 ZIP code areas lie wholly or partly in Bethlehem. On NOAA's grid 18017 is the warmest (52.2°F a year) and 18015 the coolest (52.1°F), so the city is nearly uniform. Each row also names the nearest station record and its frost dates.
| ZIP code | Zone | Year | Jan low | Jul high | Precip. | Nearest record | Last frost | First frost |
|---|---|---|---|---|---|---|---|---|
| 18015 | 7a | 52.1°F | 20°F | 86°F | 48.1 | Springtown (1 mi NNE) (5 mi) | April 21 | October 22 |
| 18017 | 7a | 52.2°F | 20°F | 86°F | 47.8 | Allentown (3 mi) | April 20 | October 24 |
| 18018 | 7a | 52.2°F | 20°F | 86°F | 47.8 | Allentown (3 mi) | April 20 | October 24 |
Source: Census Bureau 2020 ZCTA-to-place relationship file and ZCTA centers; NOAA NCEI gridded and station normals, 1991-2020. A ZIP area counts when at least a tenth of its land (and 0.5 km²) is in the city; its figures are the grid cell at its center; frost dates are the nearest record's medians of 32°F.