Hottest (avg)
#5 / 12
Sits around the middle of the year.
May in context
How it compares to the rest of the year in Boston.
Wettest (avg)
#9 / 12
Typical rainfall for the year.
Daylight Hours
#3 / 12
Long daylight hours.
Windiest (avg)
#8 / 12
Close to the yearly wind average.
Highest UV
#3 / 12
UV runs high compared with most months.
Most Humid
#8 / 12
Humidity stays close to the yearly norm.
Monthly climate breakdown
A detailed look at the typical climate conditions for May.
Thermal profile
Temperature
Typical daytime high
- Nighttime low
-
- Feels like (avg)
-
Light window
Sunshine
14.6 h
Average daylight
- UV index (max)
- 8
- Typical sun hours
- 04:22 - 18:59
Wet-day pattern
Rain & Snow
Typical rainfall
- Rainy days
- 14 days
- Cloud cover (avg)
- 63%
- Snowfall
-
Air feel
Humidity & Wind
72%
Average humidity
- Wind (avg)
-
- Wind (max gusts)
-
Historical daily baseline
Daily climate explorer
Pick a day to inspect the usual conditions through May in Boston. Based on a 30-year historical climate baseline, not a forecast.
Primary control
Select a day
Scroll to compare daily conditions. The summary updates with your selection.
Secondary context
Monthly trend
Median daytime highs across the month, with a softer low line.
Median temperatureMedian lowTypical range
Day 15 selected for May. Temperature 20.5°C.
Historical disruption baseline
Typical disruptions in May
Based on 30 years of historical data, these are the disruption patterns most likely to affect plans in May.
Cold High impact
Cold feels-like nights Measures: Cold feels-like nights (min <=5C). Observed about 38% of days (11.7 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
11.7 days / month
- Share of days
- ~38% of days
- Upper edge
- Up to ~5°C (P95)
Why this matters
Cold feels-like nights are possible on ~12 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Rain High impact
Rain disruption Measures: Likely rain disruption days. Observed about 17% of days (5.4 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
5.4 days / month
- Share of days
- ~17% of days
- Upper edge
- Up to ~30mm (P95)
Why this matters
Rain disruption risk appears on ~5 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Washout risk Measures: Washout day risk. Observed about 16% of days (5.1 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
5.1 days / month
- Share of days
- ~16% of days
- Upper edge
- Up to ~30mm (P95)
Why this matters
Washout conditions are possible on ~5 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Heavy rain days Measures: Heavy rain days (>=10mm). Observed about 9% of days (2.7 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
2.7 days / month
- Share of days
- ~9% of days
- Upper edge
- Up to ~36mm (P95)
Why this matters
Heavy rain is possible on ~3 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Wind High impact
Strong gusts Measures: Strong gust days (>=60 km/h). Observed about 5% of days (1.4 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.4 days / month
- Share of days
- ~5% of days
- Upper edge
- Up to ~80km/h (P95)
Why this matters
Strong gusts are possible on ~1 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Wind High impact
Stormy conditions Measures: Storm-impact proxy days. Observed about 4% of days (1.1 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.1 days / month
- Share of days
- ~4% of days
- Upper edge
- Up to ~79km/h (P95)
Why this matters
Stormy conditions are possible on ~1 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Show all disruptions (19 more)
Rain High impact
Washout run Measures: Multi-day washout runs. Observed about 1.1 days/month in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.1 days / month
- Share of days
- —
- Upper edge
- Up to ~33mm (P95)
Why this matters
Multi-day washout runs are possible on ~1 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Very heavy rain Measures: Very heavy rain days (>=25mm). Observed about 2% of days (0.5 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.5 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~51mm (P95)
Why this matters
Very heavy rain is possible on ~0 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Visibility Moderate
Fog-likely signal Measures: Fog-likely visibility proxy. Observed about 9% of days (2.8 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
2.8 days / month
- Share of days
- ~9% of days
- Upper edge
- Up to ~98% (P95)
Why this matters
Fog-likely conditions are possible on ~3 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Heat Moderate
Hot feels-like days Measures: Hot feels-like days (>=32C). Observed about 2% of days (0.8 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.8 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~36°C (P95)
Why this matters
Feels-like heat >=32C is possible on ~1 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Cloud Minor
Cloudy days Measures: Cloudy days (cloud cover >=60%). Observed about 57% of days (17.5 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
17.5 days / month
- Share of days
- ~57% of days
- Upper edge
- Up to ~100% (P95)
Why this matters
Cloudy skies are possible on ~18 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Rain Minor
Wet days Measures: Wet days (>=0.1mm). Observed about 51% of days (15.8 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
15.8 days / month
- Share of days
- ~51% of days
- Upper edge
- Up to ~20mm (P95)
Why this matters
Measurable rain is possible on ~16 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Wind Minor
Gusty days Measures: Gusty days (>=40 km/h). Observed about 43% of days (13.2 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
13.2 days / month
- Share of days
- ~43% of days
- Upper edge
- Up to ~65km/h (P95)
Why this matters
Gusty conditions are possible on ~13 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Rain Minor
Rainy hours Measures: Rain-hours signal (>=3h rain). Observed about 39% of days (12.0 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
12.0 days / month
- Share of days
- ~39% of days
- Upper edge
- Up to ~20h (P95)
Why this matters
Several rainy hours are possible on ~12 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Cloud Minor
Mostly cloudy days Measures: Mostly cloudy days (cloud cover >=80%). Observed about 37% of days (11.6 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
11.6 days / month
- Share of days
- ~37% of days
- Upper edge
- Up to ~100% (P95)
Why this matters
Mostly cloudy skies are possible on ~12 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Humidity Minor
High humidity Measures: High humidity days (RH >=80%). Observed about 35% of days (10.7 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
10.7 days / month
- Share of days
- ~35% of days
- Upper edge
- Up to ~97% (P95)
Why this matters
High humidity is possible on ~11 days. Comfort and pace can drop quickly, so plan shorter outdoor blocks with air-conditioned backup stops.
Rain Minor
Wet most of day Measures: Wet-most-of-day signal (>=6h rain). Observed about 26% of days (8.0 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
8.0 days / month
- Share of days
- ~26% of days
- Upper edge
- Up to ~22h (P95)
Why this matters
Wet-most-of-day conditions are possible on ~8 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Cloud Minor
Overcast days Measures: Overcast days (cloud cover >=95%). Observed about 19% of days (5.9 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
5.9 days / month
- Share of days
- ~19% of days
- Upper edge
- Up to ~100% (P95)
Why this matters
Overcast skies are possible on ~6 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Other Minor
Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data Measures: Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data. Observed about 9% of days (2.8 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
2.8 days / month
- Share of days
- ~9% of days
- Upper edge
- Up to ~98 (P95)
Why this matters
Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data is possible on ~3 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Cold Minor
Cold nights Measures: Cold nights (min <=5C). Observed about 8% of days (2.5 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
2.5 days / month
- Share of days
- ~8% of days
- Upper edge
- Up to ~5°C (P95)
Why this matters
Cold nights are possible on ~3 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Cold Minor
Cold days Measures: Cold days (max <=10C). Observed about 3% of days (1.0 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.0 days / month
- Share of days
- ~3% of days
- Upper edge
- Up to ~10°C (P95)
Why this matters
Cold daytime conditions are possible on ~1 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Heat Minor
Hot days Measures: Hot days (>=30C). Observed about 3% of days (0.8 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.8 days / month
- Share of days
- ~3% of days
- Upper edge
- Up to ~34°C (P95)
Why this matters
Hot days are possible on ~1 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Wind Minor
Breezy days Measures: Breezy days (mean wind >=25 km/h). Observed about 2% of days (0.6 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.6 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~34km/h (P95)
Why this matters
Breezy conditions are possible on ~1 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Humidity Minor
Humid days Measures: Humid days (dew point >=18C). Observed about 2% of days (0.5 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.5 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~20°C (P95)
Why this matters
Humid conditions are possible on ~0 days. Comfort and pace can drop quickly, so plan shorter outdoor blocks with air-conditioned backup stops.
Cold Minor
Wind chill risk Measures: Wind chill risk days. Observed about 1% of days (0.2 days/month) in May. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.2 days / month
- Share of days
- ~1% of days
- Upper edge
- Up to ~-0°C (P95)
Why this matters
Wind chill risk is possible on ~0 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Travel planning FAQ
Frequently asked questions
Quick answers to the weather questions you ask the most.
Is May a good time to visit Boston?
Typical May days in Boston reach highs of 19°C (66°F) with nights around 9°C (48°F). It usually feels mild by day and cool after dark. Overall, May sits in the middle of the Boston climate range.
What are temperatures like in May?
In May, you can usually expect highs of 19°C (66°F) and lows near 9°C (48°F). That means mild days and cool nights, so pack layers you can add or remove.
How much does it rain in May?
Rainfall in May averages 86 mm (3.4 in) across roughly 14 days. Overall it is a quite rainy time of year, so a light rain jacket and waterproof shoes are very handy.
How many hours of daylight are there in May?
You can expect about 15 hours of daylight in May. Sunrise is typically around 04:22 and sunset near 18:59. You get long days with comfortable amounts of daylight.
How strong is the sun in May?
UV levels are often high (around 8). Regular sunscreen and a hat are recommended.
Is it windy in May?
In May, average wind speeds are around 13 km/h (8 mph), with gusts on the windiest days reaching about 54 km/h (34 mph). On the ground, it is it can feel quite windy at times, particularly when weather systems move through.