Frost Advisory
Starts in 1 h 55 min
When
From midnight tonight to 9 AM EDT Sunday.
Where
In Connecticut, Southern Fairfield, Southern Middlesex, Southern New Haven, and Southern New London Counties. In New York, Northeast Suffolk and Southeast Suffolk Counties.
Issued for this forecast zone · National Weather Service Upton NY
What, impacts and precautionsHide details
What
Temperatures in the mid 30s, and locally as low 25 to 30 in parts of the Pine Barrens of Long Island, will result in frost formation.
Impacts
Frost could harm sensitive outdoor vegetation. Sensitive outdoor plants may be killed if left uncovered.
Precautionary actions
Take steps now to protect tender plants from the cold.
Areas: Southern Fairfield; Southern New Haven; Southern Middlesex; Southern New London; Northeast Suffolk; Southeast Suffolk
See it on weather.gov (opens in a new tab)

Observed 9:50 PM EDT at KHPN

Cos Cob, CT weather

Clear and 45°7°.

Forecasts agree

Now 45°7°

Clear

Wind: Calm; Light through 10 AM
Dew point: 37°3°; Comfortable
UV tomorrow: 4Moderate; Moderate 11 AM–4 PM · peak 4
Air today: 50Good; EPA forecast · PM2.5 (fine particles)
Pressure: 30.54 inHg1034 hPa; Rising slowly · +0.02 inHg+0.6 hPa in 3 h

No precipitation expected in the next 2 hours.

From forecast models

Next 48 hours

4°2° cooler than this time yesterday (49°9° then, 45°7° now)

Good hours for

Low 39°4° tonight at 4 AM
Above 50°10° tomorrow by 10 AM
High 66°19° tomorrow at 4 PM
Below 50°10° tomorrow night after 9 PM

TonightDown to 39°4° by 4 AM · Clear
Tomorrow morningUp to 58°14° by 11 AM · Clear
Tomorrow afternoonUp to 66°19° by 4 PM · Clear
Tomorrow nightDown to 42°6° by 5 AM · Clear
Monday morningUp to 60°16° by 11 AM · Clear
Monday afternoonUp to 69°21° by 3 PM · Clear
Monday nightDown to 56°13° by 9 PM · Clear

Hourly forecast, next 48 hours, in the place's local time
Hour	Conditions	Temperature	Feels like	Precipitation	Wind	Humidity	Cloud cover	UV index
Sat 10p	Clear	44°7° (likely 44°7° to 51°11°)	44°7°	0%	1 mph2 km/h from NW, gusts 4 mph7 km/h	65%	1%	0
Sat 11p	Clear	43°6° (likely 43°6° to 49°9°)	43°6°	0%	1 mph2 km/h from NW, gusts 5 mph7 km/h	67%	2%	0
Sun 12a	Clear	41°5° (likely 41°5° to 47°8°)	41°5°	0%	1 mph2 km/h from NW, gusts 5 mph9 km/h	73%	2%	0
Sun 1a	Clear	41°5° (likely 40°4° to 46°8°)	41°5°	0%	2 mph3 km/h from NW, gusts 5 mph8 km/h	73%	0%	0
Sun 2a	Clear	40°4° (likely 38°3° to 45°7°)	40°4°	0%	2 mph3 km/h from NW, gusts 6 mph9 km/h	76%	0%	0
Sun 3a	Clear	40°4° (likely 37°3° to 44°7°)	40°4°	0%	2 mph3 km/h from NW, gusts 6 mph10 km/h	76%	1%	0
Sun 4a	Clear	39°4° (likely 37°3° to 43°6°)	37°3°	0%	3 mph5 km/h from NW, gusts 7 mph11 km/h	76%	0%	0
Sun 5a	Clear	39°4° (likely 37°3° to 42°6°)	37°3°	0%	3 mph5 km/h from NW, gusts 7 mph12 km/h	76%	0%	0
Sun 6a	Clear	39°4° (likely 36°2° to 42°6°)	37°3°	0%	3 mph5 km/h from NW, gusts 7 mph11 km/h	76%	0%	0
Sun 7a	Sunny	39°4° (likely 36°2° to 42°6°)	37°3°	0%	3 mph5 km/h from N, gusts 6 mph9 km/h	79%	0%	0
Sun 8a	Sunny	40°4° (likely 37°3° to 43°6°)	38°3°	0%	3 mph5 km/h from N, gusts 7 mph11 km/h	79%	0%	0
Sun 9a	Sunny	47°8° (likely 44°7° to 47°8°)	46°8°	0%	3 mph5 km/h from NW, gusts 6 mph10 km/h	63%	0%	1
Sun 10a	Sunny	54°12° (likely 52°11° to 55°13°)	54°12°	0%	2 mph3 km/h from NW, gusts 5 mph7 km/h	50%	0%	2
Sun 11a	Sunny	58°14° (likely 57°14° to 60°16°)	58°14°	0%	2 mph3 km/h from NW, gusts 5 mph8 km/h	45%	0%	3
Sun 12p	Sunny	62°17° (likely 60°16° to 63°17°)	62°17°	0%	2 mph3 km/h from W, gusts 6 mph10 km/h	39%	0%	4
Sun 1p	Sunny	64°18° (likely 62°17° to 65°18°)	64°18°	0%	3 mph5 km/h from SW, gusts 7 mph12 km/h	37%	0%	4
Sun 2p	Sunny	65°18° (likely 63°17° to 66°19°)	65°18°	0%	3 mph5 km/h from SW, gusts 8 mph13 km/h	37%	0%	4
Sun 3p	Sunny	65°18° (likely 64°18° to 66°19°)	65°18°	0%	3 mph5 km/h from SW, gusts 8 mph13 km/h	37%	0%	3
Sun 4p	Sunny	66°19° (likely 63°17° to 66°19°)	66°19°	0%	2 mph3 km/h from SW, gusts 8 mph12 km/h	36%	0%	2
Sun 5p	Sunny	65°18° (likely 62°17° to 65°18°)	65°18°	0%	2 mph3 km/h from SW, gusts 8 mph12 km/h	38%	0%	1
Sun 6p	Clear	61°16° (likely 57°14° to 61°16°)	61°16°	0%	2 mph3 km/h from SW, gusts 8 mph12 km/h	44%	0%	0
Sun 7p	Clear	57°14° (likely 54°12° to 57°14°)	57°14°	0%	2 mph3 km/h from SW, gusts 6 mph10 km/h	53%	0%	0
Sun 8p	Clear	51°11° (likely 51°11° to 55°13°)	51°11°	0%	2 mph3 km/h from SW, gusts 7 mph11 km/h	68%	0%	0
Sun 9p	Clear	49°9° (likely 49°9° to 53°12°)	49°9°	0%	2 mph3 km/h from SW, gusts 8 mph12 km/h	74%	0%	0
Sun 10p	Clear	48°9° (likely 47°8° to 51°11°)	47°8°	0%	3 mph5 km/h from W, gusts 6 mph10 km/h	77%	0%	0
Sun 11p	Clear	47°8° (likely 46°8° to 50°10°)	46°8°	0%	3 mph5 km/h from W, gusts 7 mph11 km/h	79%	0%	0
Mon 12a	Clear	46°8° (likely 45°7° to 50°10°)	45°7°	0%	3 mph5 km/h from W, gusts 8 mph13 km/h	83%	0%	0
Mon 1a	Clear	45°7° (likely 44°7° to 49°9°)	44°7°	0%	3 mph5 km/h from W, gusts 8 mph14 km/h	86%	0%	0
Mon 2a	Clear	44°7° (likely 42°6° to 48°9°)	42°6°	0%	3 mph5 km/h from W, gusts 9 mph14 km/h	89%	0%	0
Mon 3a	Clear	43°6° (likely 42°6° to 47°8°)	41°5°	0%	3 mph5 km/h from W, gusts 9 mph15 km/h	93%	0%	0
Mon 4a	Clear	43°6° (likely 41°5° to 47°8°)	41°5°	0%	3 mph5 km/h from W, gusts 10 mph16 km/h	93%	16%	0
Mon 5a	Clear	42°6° (likely 41°5° to 46°8°)	40°4°	0%	3 mph5 km/h from W, gusts 9 mph15 km/h	96%	0%	0
Mon 6a	Clear	42°6° (likely 40°4° to 46°8°)	40°4°	0%	3 mph5 km/h from W, gusts 9 mph15 km/h	93%	0%	0
Mon 7a	Sunny	42°6° (likely 39°4° to 46°8°)	39°4°	0%	5 mph8 km/h from W, gusts 9 mph14 km/h	93%	10%	0
Mon 8a	Sunny	43°6° (likely 39°4° to 46°8°)	40°4°	0%	5 mph8 km/h from W, gusts 9 mph14 km/h	89%	0%	0
Mon 9a	Sunny	48°9° (likely 46°8° to 49°9°)	46°8°	0%	5 mph8 km/h from W, gusts 7 mph11 km/h	77%	13%	1
Mon 10a	Sunny	54°12° (likely 53°12° to 56°13°)	54°12°	0%	5 mph8 km/h from W, gusts 10 mph17 km/h	66%	5%	2
Mon 11a	Sunny	60°16° (likely 57°14° to 61°16°)	60°16°	0%	5 mph8 km/h from W, gusts 11 mph18 km/h	58%	14%	3
Mon 12p	Sunny	64°18° (likely 61°16° to 65°18°)	64°18°	0%	5 mph8 km/h from W, gusts 11 mph18 km/h	52%	6%	4
Mon 1p	Sunny	67°19° (likely 63°17° to 67°19°)	67°19°	0%	6 mph10 km/h from W, gusts 11 mph18 km/h	50%	1%	4
Mon 2p	Sunny	68°20° (likely 67°19° to 69°21°)	68°20°	0%	6 mph10 km/h from W, gusts 12 mph19 km/h	51%	1%	4
Mon 3p	Sunny	69°21° (likely 67°19° to 69°21°)	69°21°	0%	6 mph10 km/h from W, gusts 12 mph20 km/h	51%	5%	3
Mon 4p	Sunny	69°21° (likely 67°19° to 69°21°)	69°21°	0%	5 mph8 km/h from W, gusts 13 mph21 km/h	53%	2%	2
Mon 5p	Sunny	67°19° (likely 67°19° to 68°20°)	67°19°	0%	5 mph8 km/h from W, gusts 10 mph17 km/h	59%	0%	1
Mon 6p	Clear	64°18° (likely 62°17° to 64°18°)	64°18°	0%	5 mph8 km/h from W, gusts 8 mph12 km/h	65%	0%	0
Mon 7p	Clear	60°16° (likely 58°14° to 61°16°)	60°16°	0%	6 mph10 km/h from W, gusts 9 mph15 km/h	72%	1%	0
Mon 8p	Clear	57°14° (likely 55°13° to 60°16°)	57°14°	0%	6 mph10 km/h from W, gusts 12 mph19 km/h	77%	3%	0
Mon 9p	Clear	56°13° (likely 54°12° to 59°15°)	56°13°	0%	6 mph10 km/h from NW, gusts 13 mph21 km/h	80%	11%	0

Days ahead

Shaded: typical range for these dates (1991–2020)

Today, Oct 24. Cloudy. High 61°16°, low 39°4°. Typical 60°16° / 43°6°. Dry. Forecasts agree.
1. Evening
  6 PM–midnight
  Clear, 43°6°
  Dry
2. Overnight
  midnight–6 AM
  Clear, 39°4°
  Dry
Official NWS forecast
Tonight: Clear, with a low around 39. Northwest wind around 3 mph.
Forecasts agreeIndependent forecasts are close; the range is narrow.
High, likely
60°16°–62°17°
Low, likely
33°1°–39°4°
Typical high / low
60°16° / 43°6°
Wind
7 mph11 km/h, gusts 13 mph22 km/h
UV peak
4
Tomorrow, Oct 25. Sunny. High 66°19°, low 42°6°. Typical 60°16° / 42°6°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 40°4°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 66°19°
  Dry
3. Evening
  6 PM–midnight
  Clear, 51°11°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 42°6°
  Dry
Official NWS forecast
Day: Sunny, with a high near 66. West wind around 3 mph.
Night: Clear, with a low around 42. West wind around 3 mph.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
64°18°–66°19°
Low, likely
36°2°–42°6°
Typical high / low
60°16° / 42°6°
Wind
6 mph10 km/h
UV peak
4
Monday, Oct 26. Sunny. High 69°21°, low 46°8°. Typical 59°15° / 42°6°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 43°6°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 69°21°
  Dry
3. Evening
  6 PM–midnight
  Clear, 57°14°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 49°10°
  Dry
Official NWS forecast
Day: Sunny. High near 69, with temperatures falling to around 67 in the afternoon. West wind around 6 mph.
Night: Mostly clear. Low around 46, with temperatures rising to around 48 overnight. Northwest wind 5 to 8 mph.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
66°19°–69°21°
Low, likely
39°4°–46°8°
Typical high / low
59°15° / 42°6°
Wind
7 mph12 km/h, gusts 24 mph38 km/h
UV peak
4
Tuesday, Oct 27. Sunny. High 61°16°, low 38°3°. Typical 59°15° / 42°6°. Dry. Forecasts agree.
1. Morning
  6 AM–noon
  Sunny, 47°8°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 58°14°
  Dry
3. Evening
  6 PM–midnight
  Clear, 45°7°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 39°4°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Sunny. High near 61, with temperatures falling to around 59 in the afternoon.
Night: Mostly clear, with a low around 38.
Forecasts agreeIndependent forecasts are close; the range is narrow.
High, likely
57°14°–61°16°
Low, likely
38°3°–46°8°
Typical high / low
59°15° / 42°6°
Wind
11 mph17 km/h, gusts 23 mph37 km/h
UV peak
4
Wednesday, Oct 28. Cloudy. High 59°15°, low 45°7°. Typical 59°15° / 42°6°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 39°4°
  Dry
2. Afternoon
  noon–6 PM
  Mostly sunny, 57°14°
  Dry
3. Evening
  6 PM–midnight
  Cloudy, 51°10°
  Dry
4. Overnight
  midnight–6 AM
  Mostly clear, 48°9°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Sunny, with a high near 59.
Night: Partly cloudy, with a low around 45.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
55°13°–60°16°
Low, likely
34°1°–45°7°
Typical high / low
59°15° / 42°6°
Wind
8 mph13 km/h, gusts 15 mph25 km/h
UV peak
4
Thursday, Oct 29. Partly sunny. High 67°19°, low 49°9°. Typical 58°14° / 41°5°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 48°9°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 66°19°
  Dry
3. Evening
  6 PM–midnight
  Clear, 58°14°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 52°11°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Mostly sunny, with a high near 67.
Night: Mostly clear, with a low around 49.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
63°17°–67°19°
Low, likely
46°8°–49°9°
Typical high / low
58°14° / 41°5°
Wind
9 mph15 km/h, gusts 28 mph45 km/h
UV peak
4
Friday, Oct 30. Mostly sunny. High 71°22°, low 49°9°. Typical 58°14° / 41°5°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 52°11°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 72°22°
  Dry
3. Evening
  6 PM–midnight
  Clear, 59°15°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 49°10°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Sunny, with a high near 71.
Night: Mostly clear, with a low around 49.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
69°21°–74°23°
Low, likely
47°8°–54°12°
Typical high / low
58°14° / 41°5°
Wind
10 mph17 km/h, gusts 21 mph34 km/h
UV peak
4
Saturday, Oct 31. Partly sunny. High 68°20°, low 49°9°. Typical 58°14° / 41°5°. Dry. Forecasts differ.
1. Morning
  6 AM–noon
  Sunny, 50°10°
  Dry
2. Afternoon
  noon–6 PM
  Mostly sunny, 65°19°
  Dry
3. Evening
  6 PM–midnight
  Cloudy, 55°13°
  Dry
4. Overnight
  midnight–6 AM
  Cloudy, 53°12°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Mostly sunny, with a high near 68.
Forecasts differIndependent forecasts disagree; expect changes and plan for the range.
High, likely
59°15°–69°21°
Low, likely
46°8°–51°11°
Typical high / low
58°14° / 41°5°
Wind
7 mph12 km/h, gusts 20 mph33 km/h
UV peak
4
Sunday, Nov 1. Drizzle. High 66°19°, low 53°12°. Typical 57°14° / 40°4°. Rain 0.01 in0.3 mm, 30% chance. Forecasts differ.
1. Morning
  6 AM–noon
  Cloudy, 54°12°
  Dry
2. Afternoon
  noon–6 PM
  Cloudy, 67°19°
  Dry
3. Evening
  6 PM–midnight
  Drizzle, 62°17°
  30% chance · 0.02 in0.5 mm
4. Overnight
  midnight–6 AM
  Drizzle, 61°16°
  40% chance · 0.13 in3.3 mm
Hours this far out come from computer models only.
The National Weather Service writes about seven days ahead; this day is our model forecast only.
Forecasts differIndependent forecasts disagree; expect changes and plan for the range.
High, likely
63°17°–71°22°
Low, likely
49°9°–55°13°
Typical high / low
57°14° / 40°4°
Wind
10 mph17 km/h, gusts 26 mph41 km/h
UV peak
3
Monday, Nov 2. Drizzle. High 66°19°, low 59°15°. Typical 57°14° / 40°4°. Rain 0.26 in6.6 mm, 40% chance. Mostly agree.
1. Morning
  6 AM–noon
  Drizzle, 62°17°
  40% chance · 0.09 in2.2 mm
2. Afternoon
  noon–6 PM
  Drizzle, 66°19°
  30% chance · 0.05 in1.3 mm
3. Evening
  6 PM–midnight
  Drizzle, 62°17°
  30% chance · 0.02 in0.6 mm
Hours this far out come from computer models only.
The National Weather Service writes about seven days ahead; this day is our model forecast only.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
64°18°–71°22°
Low, likely
55°13°–64°18°
Typical high / low
57°14° / 40°4°
Wind
17 mph27 km/h, gusts 35 mph56 km/h

10 days15 days30 days

The outlook

Today
Dry, high 61°, low 39°.
Tomorrow
Dry, high 66°, low 42°, warming up.
Monday
Dry, high 69°, low 46°, warming up.
Rest of week
Mostly dry, highs 59–71°.

Want the meteorologists’ reasoning? Read the NWS forecast discussion (OKX) (opens in a new tab)

What changed since yesterday

No meaningful changes from yesterday’s forecast.

Radar

Radar data: NOAA MRMS, rendered by forecast.blue

Radar loads when scrolled into view

Full-screen radar

Rivers

NOAA river gauges within 25 mi

Little Neck Bay at Kings Point (IN MLLW)

19 mi

Below flood stage

Level: 6.5 ft

Forecast peak 10.2 ft Tue 12 PM, minor flooding

Reading from Sat 8:36 PM · NWS gauge page

Long Island Sound at Stamford (IN MLLW)

2.5 mi

Below flood stage

Level: 7.0 ft

Reading from Sat 9 PM · NWS gauge page

Rippowam River at Stamford

2.5 mi

Below flood stage

Level: 1.5 ft

Reading from Sat 8:45 PM · NWS gauge page

Long Island Sound at Rye (IN MLLW)

7.3 mi

Below flood stage

Level: 6.6 ft

Reading from Sat 8:42 PM · NWS gauge page

For your home

What this week’s weather means for heating, cooling, pipes and fresh air.

Heating this week

About 75% less heating than a typical week.

This week 26Typical 102

Heating degree days, base 65°F

Heat-pump hours, next 7 days

h below 47°F: 21
h below 17°F: 0
h below 5°F: 0

47, 17 and 5°F are the test points heat pumps are rated at. About 3 hours are near freezing and damp, when outdoor units defrost more often.

Comfort

Dry air outside (dew point 37°F).

Open the windows?

Sun, 12:00 PM–6:00 PM

Good stretch to open the windows.

Is this typical?

WESTCHESTER CO AP · official normals 1991–2020 · records 1948–2026

Oct 24, today vs a typical year

Today’s expected high is about typical for the date.

Last 7 days vs normal

On average 1°0° colder than normal (daily mean temperature).

−2°−1°MonOct 19
—TueOct 20
±0°WedOct 21
+1°ThuOct 22
−1°FriOct 23
—SatOct 24
—SunOct 25

Cos Cob weather by month: normals, records, snow and freeze dates

Sun & moon

Sun

Daylight: 10 h 44 min; Losing 2 min 30 s a day; shortest Dec 21, 1 h 31 min less
Golden hour: 5:22–6:17 PM; Morning 6:58–7:54 AM
Blue hour: 6:17–6:28 PM; Morning 6:47–6:58 AM; first light 6:47 AM

Stars tonight? Fair

Clear 10:05 PM–6:49 AM, but the moon is 99% lit and up.

Moon

Waxing gibbous

98% lit · growing

Today: sets 5:26 AM · rises 4:57 PM
Full moon: Oct 26
New moon: Nov 9

Looking northeast from Cos Cob. The highest point on the skyline is about 9,800 ft, 74 mi away.Skyline from USGS elevation data, heights drawn up to 6× taller. Sky, sun and moon as they are now.

1 active weather alert

Frost Advisory

Cos Cob, CT weather

Next 2 hours

Next 48 hours

Days ahead

The outlook

Today

Tomorrow

Monday

Rest of week

What changed since yesterday

Radar

Rivers

Little Neck Bay at Kings Point (IN MLLW)

Long Island Sound at Stamford (IN MLLW)

Rippowam River at Stamford

Long Island Sound at Rye (IN MLLW)

For your home

Heating this week

Heat-pump hours, next 7 days

Comfort

Open the windows?

Is this typical?

Oct 24, today vs a typical year

Last 7 days vs normal

Sun & moon

Sun

Stars tonight? Fair

Moon