Ontario, CA Climate: Temperature & Rain by Month
Average temperature and precipitation from NOAA NCEI 1991–2020 normals →, with a derived climate comfort score
30-year climate normals (1991-2020) from Ontario's primary NOAA station, ONTARIO INTL AP.
The climate verdict for Ontario
Dryness leads the climate profile for Ontario, California, with 11.6 inches of precipitation a year. NOAA records an annual average of 67°F. It scores 88/100 for climate comfort (excellent), putting it in the top third of station-mapped location scores and exceeding 89% of them.
- 67°F
- annual average temperature (NOAA normal)
- 88/100
- comfort score, above 89% of station-mapped location scores
- 11.6"
- yearly precipitation total
- 360 days
- frost-free days per growing season
Ontario: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USW00003102 · Ontario, CA 67°F mean · 11.6" precip
TEMP-MILD · RANK-WARM · PHOTO-FINISH · PRCP-ARID · SWING-NARROW · COMF-TOP · LOAD-MIX · STN-1 · BOOK-FULL
- TEMP-MILD 67°F
- RANK-WARM #6,312
- PHOTO-FINISH ≈ Arlington
- PRCP-ARID 11.6"
- SWING-NARROW 25°F
- COMF-TOP 88/100
- LOAD-MIX H/C balanced
- STN-1 USW00003102
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Arlington, TX (+ 0 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every CA station list.
- Ontario (this station) 67°F
- Hot Metter, GA 67°F
- Near Arlington, TX 67°F
- Near Hammond, LA 67°F
- Near Headland, AL 67°F
Climate Living Index · Ontario
Ontario: 75/100 · grade B
Ontario publishes 4 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 2 missing weights rescale to 100.
PlainClimate-derived for Ontario, not an official NOAA rating. Rankings still use Comfort Score 88/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Frost-free season | 360 days/year | 100/100 · A |
| Annual temperature balance | 66.8°F · 0.7° from 67.5°F | 96/100 · A |
| Normal heat + freeze calendar | 86 calendar days | 80/100 · B |
| Precipitation balance | 11.6 in · 23.4 from 35 in | 17/100 · F |
Ontario · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Ontario's normals sit in a dry climate class: BSh
Precipitation is low relative to temperature but above true desert thresholds: hot semi-arid steppe (BSh). Class BSh is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: dry (arid or semi-arid), specifically hot semi-arid steppe.
- Köppen code
- BSh
- Group
- Dry (arid or semi-arid)
- Warmest month
- 80.1°F
- Coldest month
- 55.2°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · balanced station
Where Ontario sits across the climate record
Three NOAA fields for Ontario's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- Top 8% warmest
- Among 6,861 stations, Ontario sits in the warmer third of annual means.
- Annual precipitation
- Drier than 91%
- Ontario's annual total ranks in the drier third of 6,352 measured normals.
- Seasonal temperature swing
- Narrower than 95%
- Warmest-to-coldest month gap for Ontario is compact versus 6,861 complete station-years.
How Ontario compares across U.S. station-mapped locations
Ontario's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
88 Top 11% score exceeds 89% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). Below this entry.
- 60–70: 1,236 station-mapped locations (20%). Below this entry.
- 70–80: 650 station-mapped locations (11%). Below this entry.
- 80–90: 921 station-mapped locations (15%). This entry sits in this band.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|
| January | 68°F (20°C) | 45°F (7°C) | 56°F (13°C) | 2.6" | 0.5 | 0.0 |
| February | 68°F (20°C) | 46°F (8°C) | 57°F (14°C) | 3.1" | 0.2 | 0.1 |
| March | 72°F (22°C) | 49°F (9°C) | 60°F (16°C) | 1.6" | 0.0 | 0.9 |
| April | 76°F (24°C) | 51°F (11°C) | 63°F (17°C) | 0.8" | 0.0 | 2.6 |
| May | 80°F (27°C) | 56°F (13°C) | 68°F (20°C) | 0.3" | 0.0 | 5.0 |
| June | 86°F (30°C) | 60°F (16°C) | 73°F (23°C) | 0.0" | 0.0 | 11.1 |
| July | 94°F (34°C) | 65°F (18°C) | 79°F (26°C) | 0.1" | 0.0 | 22.7 |
| August | 95°F (35°C) | 65°F (18°C) | 80°F (27°C) | 0.0" | 0.0 | 23.8 |
| September | 91°F (33°C) | 64°F (18°C) | 78°F (25°C) | 0.1" | 0.0 | 17.5 |
| October | 83°F (28°C) | 57°F (14°C) | 70°F (21°C) | 0.4" | 0.0 | 8.0 |
| November | 75°F (24°C) | 49°F (9°C) | 62°F (17°C) | 0.8" | 0.2 | 1.6 |
| December | 67°F (19°C) | 44°F (6°C) | 55°F (13°C) | 1.9" | 0.8 | 0.0 |
The year, day by day
The year in Ontario runs from a mild 43°F around December 15 to 95°F at the peak near August 20, and the normal low never reaches freezing on any date in the record.
When the heat sits
Normal highs reach 90°F from June 27 through September 20, covering 86 dates. The broader mild season, normal highs of 70°F or more, runs March 4 to November 28.
This counts calendar dates whose 1991–2020 normal high reaches 90°F. It is a smaller number than the 90°F+ day counts in the monthly table above, which measure how often the threshold was actually crossed in a typical year. A date can average 88°F and still exceed 90°F in half of all years.
No freezing date
Not one calendar date in the 1991–2020 record carries a normal low at or below 32°F. The coldest normal low of the year is 43°F around December 15.
Where the wet dates fall
The likeliest wet date is February 19, when 23% of years recorded at least a hundredth of an inch. The driest is June 20 at 1%. Summed across the calendar, that is about 36 wet dates a year.
The widest day
August 16 carries the biggest normal gap between afternoon and dawn, 30°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Ontario.
Where Ontario Stands Nationally
Aridity defines the water calendar: about 12 inches in a normal year lands this among the driest tenth of ranked stations.
Heat is a defining feature of the normals calendar — the normal daily high reaches 90°F on roughly 86 days a year, more than four out of five ranked stations record.
Ontario earns 2 nationally notable standings (outer quintiles) against 6,860 NOAA 1991–2020 normals stations; only those extremes render.
Monthly Precipitation
Average monthly rainfall
5.1 days with precipitation
6.4 days with precipitation
5.3 days with precipitation
3.6 days with precipitation
1.7 days with precipitation
0.3 days with precipitation
0.6 days with precipitation
0.3 days with precipitation
0.7 days with precipitation
2.2 days with precipitation
3.7 days with precipitation
5.6 days with precipitation
Ontario's wet season runs through the cold months
December, January and February carry 65% of the year's precipitation here, while June through August contribute 1%. That is the cool-season-dominant pattern of the West Coast and the higher inland West, where storm tracks swing south in winter and summer turns dry; the thermometer meanwhile shows an unusually narrow 24.9°F seasonal spread.
- Wettest month
- February, 3.1"
- Driest month
- June, 0.0"
- Wettest three months
- February, January, December (65% of the year)
Shares are computed from this station's own 1991-2020 monthly precipitation normals. A cool-season label means the December-February share reaches 35%. Where snow falls, the monthly figures above report liquid-equivalent precipitation, so a wet winter month is not necessarily a rainy one.
How Ontario's precipitation splits across the calendar
About 36 days a year record measurable precipitation here, carrying 11.6" between them, or roughly 0.33 inches on a typical wet day. That sits in the middle band: neither the many-light-days pattern of the Pacific Northwest and the Great Lakes, nor the few-heavy-events pattern of the Gulf and the desert Southwest.
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year and say nothing about the heaviest single storm on record.
Frost Dates & Growing Season
First Fall Freeze
December 30
50% probability date
Last Spring Freeze
January 4
50% probability date
Growing Season
360 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
1,293
Higher = more heating needed
Cooling Degree Days
1,970
Higher = more cooling needed
Warmest Month
August
Coldest Month
December
Nationwide similar cities
Other rankable U.S. places outside CA closest to Ontario on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (67°F here).
- Arlington, TX 67°F · 0.0°F off
- Hammond, LA 67°F · 0.0°F off
- Headland, AL 67°F · 0.0°F off
- Metter, GA 67°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (11.6" here), excluding temperature-peer places.
- La Verkin, UT 11.6" · 0.0" off
- Fairbanks, AK 11.7" · 0.0" off
- Omak, WA 11.6" · 0.0" off
- Ephraim, UT 11.7" · 0.0" off
Scarce-water calendar
Where Ontario's limited precipitation lands
mixed demand · dry · low swing
Local precipitation is sparse in this otherwise mixed profile. The station reports 11.6 inches annually, within PlainClimate's dry band. Snowfall is not added to the interpretation because its annual value is missing. The monthly distribution matters because the total alone does not reveal the timing.
The calendar stays thermally compact and dry. August and December mark the typical warm and cold ends of the calendar, only 24.9°F apart, while the annual precipitation total remains below PlainClimate's dry threshold. The annual average is 67°F. The monthly rows show whether that limited precipitation is spread through the year or concentrated in a shorter interval.
Ontario combines a compact 24.9°F annual temperature range with meaningful demand on both sides of the thermostat: 1,293 heating and 1,970 cooling degree days. The balance matters more here than either annual total in isolation.
Ontario has a long frost-free window of roughly 360 days, but the dry annual profile is a separate constraint. Growing-season length says when freezes are unlikely, not whether rainfall is sufficient.
Ontario wettest normal
February
February concentrates the scarce annual total (11.6 inches).
Ontario driest normal
June
June is typically driest; arid stations are defined by when water is absent, not by a four-season grid.
Questions about Ontario's climate
How dry is Ontario? ▼
How many days above 90°F does Ontario get? ▼
How much energy does heating and cooling require in Ontario? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Ontario's primary station: ONTARIO INTL AP (USW00003102). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The 2024 Census Gazetteer identifies the exact name-and-state match as an incorporated place (GEOID 0653896). Match rule for Ontario: exact normalized name + state only, no fuzzy expansion, so nearby differently spelled facilities stay unmatched.
On this page every temperature, precipitation, and derived score for Ontario comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.