Ontario, CA weather in May
In May, Ontario sees highs around 80°F and lows around 56°F: warm and dry. There are about 2 days with rain. Great for outdoor plans.
- Normal high
- 80°F
- Normal low
- 56°F
- Wet days
- 2
- 0.3 in total
- Muggy days
- 0
- dew point 65°F+
How May changes from start to finish
| May 1 | May 31 | |
|---|---|---|
| Normal high | 78°F | 82°F |
| Normal low | 54°F | 57°F |
| Chance of a wet day | 8% | 4% |
| Sunrise / sunset | 6:01 am / 7:34 pm | 5:40 am / 7:56 pm |
| Daylight | 13.6 h | 14.3 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Pacific Time).
A typical May day
- 6 am56°Fdew point 50°F
- 9 am67°Fdew point 49°F
- Noon76°Fdew point 47°F
- 3 pm78°Fdew point 48°F
- 6 pm71°Fdew point 49°F
- 9 pm61°Fdew point 50°F
NOAA hourly normals (local standard time) from March AFB (26 mi away); average wind 6 mph; clear or few clouds in 65% of daytime hours, mostly cloudy or overcast in 26%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F16 of 31
- Hot dayshigh 90°F or more5 of 31
- Muggy daysdaily mean dew point 65°F or more0 of 31
- Wet daysat least 0.01 in of rain or melted snow2 of 31
- Notable rainat least 0.10 in1 of 31
- Freezing nightslow 32°F or below0 of 31
Average days per May, counted from daily records for each year 1991-2020.
Rain in May
Normal precipitation is 0.3 in; a dry May brings about 0.02 in and a wet one about 0.4 in (25th and 75th percentiles). Days with half an inch or more are rare.
How May varies from year to year
- Warmest May, 1991-20202020: average high 85°F
- Coolest May2015: average high 75°F
- Wettest May2016: 1.3 in
- Driest May1999: no measurable precipitation
- Highest reading103°F (May 13, 2013)
- Lowest reading42°F (May 1, 1999)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
May compared with April and June
| April | May | June | |
|---|---|---|---|
| Normal high | 76°F | 80°F | 86°F |
| Normal low | 51°F | 56°F | 60°F |
| Wet days | 4 | 2 | 0 |
| Comfortable days | 16 | 16 | 7 |
| Daylight | 13.1 h | 13.9 h | 14.4 h |
Highs change by +4°F from April and +6°F into June.
Nearby alternatives in May
- Warmer: Palm Springs, CA65 mi · high 95°F · 0 wet days
- Cooler: West Covina, CA16 mi · high 74°F · 4 wet days
How Ontario ranks in May
- Normal high143rd warmest of 378 cities; 22nd of 60 in California
- Wet days27th driest of 378
- Comfortable days53rd most of 339
Heating and cooling
May has 37 heating degree days and 121 cooling degree days (base 65°F), 5% of the year's total heating and cooling demand.
Questions
How hot is Ontario in May?
The normal high is 80°F and the normal low is 56°F. From 1991 to 2020 the hottest May reading was 103°F (most recently on May 13, 2013).
Does it rain a lot in Ontario in May?
About 2 days in May have at least 0.01 in of precipitation, and the normal total is 0.3 in. The wettest May in 1991-2020 was in 2016 (1.3 in); the driest was in 1999, with no measurable precipitation.
Is May a good time to visit Ontario?
May ranks 1st of 12 months on our comfort score for Ontario (74 out of 100). It has about 16 comfortable days and about 5 days at 90°F or hotter. The best months are March, April and May.
Where the numbers come from
- Temperature, rain and frost dates: Ontario Intl Airport (USW00003102), 2.9 mi E of the city center, 949 ft (52 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Snowfall and snow depth: San Gabriel Canyon PH (USC00047776), 16 mi WNW of the city center, 744 ft (257 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour and cloud cover: March AFB (USW00023119), 26 mi ESE of the city center, 1,516 ft (515 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: March Air Reserve Base (722860-23119), 26 mi ESE of the city center, 1,536 ft (535 ft higher than the city). Hourly observations, 1991-2020.