Houghton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Houghton clear sky chart from 2005-11-06 to 2024-01-15.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	13% 10% 5% 9% 7% 4 5% 5% 5% 6% 31%	74795
	Night	13% 12% 5% 10% 8% 4 5% 4 4 5% 26%	74996
Transparency	Day	54% 4 12% 21% 9% 1	74501
	Night	60% 4 11% 18% 7% 1	74824
Seeing	Day	19% 11% 31% 25% 11% 3	14930
	Night	20% 11% 28% 28% 12% 1	24963

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	9% 16% 11% 18% 14% 7% 8% 3 4 3 8%	1517
	11th to 20th	Day	12% 16% 8% 15% 14% 10% 8% 3 4 2 8%	1472
	21st to end	Day	10% 13% 9% 15% 15% 9% 7% 6% 4 3 10%	1584
February	1st to 10th	Day	8% 12% 6% 13% 16% 8% 10% 5% 5% 4 12%	1526
	11th to 20th	Day	8% 12% 7% 13% 10% 8% 8% 5% 4 4 19%	1644
	21st to end	Day	9% 14% 7% 13% 12% 5% 6% 5% 6% 6% 16%	1480
March	1st to 10th	Day	9% 11% 6% 11% 10% 4 7% 5% 6% 6% 25%	1798
	11th to 20th	Day	11% 11% 5% 10% 8% 4 4 4 4 6% 33%	1858
	21st to end	Day	15% 11% 6% 11% 7% 4 5% 5% 5% 6% 26%	2376
April	1st to 10th	Day	14% 11% 6% 7% 6% 4 5% 7% 5% 7% 29%	2160
	11th to 20th	Day	19% 10% 5% 8% 6% 4 4 4 4 6% 29%	2138
	21st to end	Day	18% 9% 4 6% 6% 3 4 5% 5% 6% 35%	2340
May	1st to 10th	Day	14% 9% 4 6% 5% 3 5% 5% 5% 7% 37%	2510
	11th to 20th	Day	13% 7% 3 6% 6% 4 5% 4 5% 7% 39%	2479
	21st to end	Day	12% 7% 3 6% 6% 3 4 5% 6% 9% 39%	2725
June	1st to 10th	Day	10% 6% 2 5% 5% 3 5% 5% 6% 8% 44%	2520
	11th to 20th	Day	12% 5% 3 5% 5% 3 4 5% 6% 8% 43%	2520
	21st to end	Day	13% 6% 2 5% 4 2 5% 5% 6% 8% 44%	2520
July	1st to 10th	Day	7% 4 2 4 4 2 4 5% 6% 9% 53%	2520
	11th to 20th	Day	8% 5% 2 5% 5% 2 4 5% 6% 8% 49%	2520
	21st to end	Day	8% 5% 2 4 4 3 4 4 5% 8% 53%	2743
August	1st to 10th	Day	9% 4 2 5% 5% 2 4 5% 7% 9% 49%	2507
	11th to 20th	Day	11% 6% 2 5% 5% 3 4 5% 5% 7% 48%	2384
	21st to end	Day	12% 6% 3 5% 4 3 5% 5% 5% 7% 47%	2376
September	1st to 10th	Day	15% 6% 2 5% 5% 4 4 4 6% 8% 43%	2160
	11th to 20th	Day	14% 8% 3 6% 5% 3 4 4 6% 9% 39%	2084
	21st to end	Day	20% 8% 3 6% 6% 3 4 3 5% 7% 33%	1980
October	1st to 10th	Day	17% 13% 4 8% 7% 3 4 3 4 7% 30%	1854
	11th to 20th	Day	22% 18% 4 8% 5% 4 5% 5% 4 6% 19%	1731
	21st to end	Day	21% 22% 7% 8% 8% 3 4 3 3 4 17%	1782
November	1st to 10th	Day	17% 19% 7% 10% 6% 4 4 5% 3 5% 21%	1672
	11th to 20th	Day	16% 19% 9% 15% 10% 4 4 4 3 3 12%	1578
	21st to end	Day	12% 20% 10% 19% 12% 3 4 5% 3 4 9%	1520
December	1st to 10th	Day	9% 18% 13% 22% 12% 4 4 3 4 4 7%	1520
	11th to 20th	Day	15% 15% 10% 18% 14% 6% 5% 4 3 3 7%	1914
	21st to end	Day	21% 19% 9% 16% 10% 4 5% 3 2 4 8%	2783
January	1st to 10th	Night	9% 15% 10% 18% 13% 7% 8% 4 3 3 9%	2648
	11th to 20th	Night	11% 14% 8% 17% 17% 7% 7% 4 3 4 8%	2583
	21st to end	Night	11% 14% 9% 15% 15% 9% 8% 6% 3 3 6%	2772
February	1st to 10th	Night	10% 13% 6% 13% 13% 9% 10% 5% 4 3 15%	2430
	11th to 20th	Night	10% 11% 5% 12% 12% 8% 11% 5% 5% 5% 18%	2202
	21st to end	Night	12% 15% 6% 11% 9% 6% 7% 4 5% 5% 21%	1776
March	1st to 10th	Night	9% 10% 4 11% 8% 4 6% 5% 6% 6% 31%	2149
	11th to 20th	Night	11% 11% 6% 9% 7% 4 5% 4 5% 6% 34%	2117
	21st to end	Night	15% 10% 4 8% 6% 3 4 5% 5% 7% 32%	1980
April	1st to 10th	Night	17% 10% 5% 8% 6% 5% 7% 6% 5% 6% 25%	1800
	11th to 20th	Night	19% 11% 4 7% 5% 3 5% 4 5% 6% 32%	1771
	21st to end	Night	18% 10% 4 6% 6% 2 5% 4 4 6% 34%	1620
May	1st to 10th	Night	16% 8% 4 7% 7% 4 5% 5% 5% 6% 32%	1446
	11th to 20th	Night	15% 9% 4 6% 6% 3 5% 4 4 6% 37%	1416
	21st to end	Night	12% 7% 2 6% 6% 4 6% 6% 7% 8% 37%	1551
June	1st to 10th	Night	14% 5% 3 6% 5% 3 6% 5% 5% 7% 41%	1440
	11th to 20th	Night	11% 7% 4 5% 6% 4 6% 7% 6% 7% 37%	1440
	21st to end	Night	14% 5% 3 5% 5% 3 6% 5% 6% 8% 40%	1440
July	1st to 10th	Night	8% 3 3 5% 5% 3 5% 4 5% 8% 51%	1440
	11th to 20th	Night	10% 5% 3 4 5% 3 5% 5% 6% 8% 45%	1440
	21st to end	Night	8% 4 3 4 5% 3 4 5% 6% 9% 49%	1575
August	1st to 10th	Night	9% 4 2 4 6% 3 4 6% 7% 7% 48%	1432
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 6% 7% 50%	1512
	21st to end	Night	13% 6% 2 5% 4 3 3 4 4 7% 49%	1980
September	1st to 10th	Night	13% 5% 3 5% 4 3 4 5% 5% 7% 47%	1800
	11th to 20th	Night	12% 7% 3 6% 6% 3 5% 4 5% 7% 42%	1858
	21st to end	Night	18% 8% 3 7% 5% 3 4 4 5% 6% 36%	1980
October	1st to 10th	Night	19% 9% 2 7% 6% 3 4 4 4 6% 35%	2105
	11th to 20th	Night	18% 16% 4 8% 7% 4 5% 4 5% 5% 24%	2228
	21st to end	Night	20% 19% 5% 9% 6% 3 4 4 4 4 22%	2574
November	1st to 10th	Night	15% 20% 5% 8% 7% 3 4 4 5% 6% 21%	2406
	11th to 20th	Night	16% 17% 8% 14% 9% 4 5% 4 4 4 16%	2598
	21st to end	Night	15% 16% 10% 17% 10% 3 5% 4 3 4 14%	2660
December	1st to 10th	Night	11% 17% 11% 22% 11% 4 5% 3 3 3 10%	2660
	11th to 20th	Night	10% 17% 8% 17% 12% 6% 6% 5% 4 4 12%	3283
	21st to end	Night	19% 21% 9% 15% 9% 4 4 3 2 3 10%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	82% 3 6% 8% 1	1518
	11th to 20th	Day	83% 3 6% 7% 1	1472
	21st to end	Day	80% 4 6% 8% 2	1584
February	1st to 10th	Day	74% 4 11% 10% 1	1526
	11th to 20th	Day	70% 3 9% 15% 4	1653
	21st to end	Day	67% 5% 7% 12% 8% 1	1480
March	1st to 10th	Day	57% 5% 12% 15% 9% 1	1800
	11th to 20th	Day	54% 3 13% 18% 11% 1	1858
	21st to end	Day	58% 5% 10% 18% 8% 1	2376
April	1st to 10th	Day	53% 6% 10% 22% 9% 1	2160
	11th to 20th	Day	57% 4 8% 21% 9% 2	2138
	21st to end	Day	50% 4 9% 22% 13% 2	2340
May	1st to 10th	Day	46% 4 13% 23% 13% 1	2510
	11th to 20th	Day	45% 3 10% 28% 13% 1	2483
	21st to end	Day	42% 5% 15% 24% 13% 1	2725
June	1st to 10th	Day	38% 3 17% 28% 13% 1	2520
	11th to 20th	Day	39% 4 15% 26% 14% 1	2520
	21st to end	Day	38% 4 16% 29% 12% 1	2520
July	1st to 10th	Day	28% 3 15% 37% 16% 1	2451
	11th to 20th	Day	33% 4 15% 32% 15% 2	2445
	21st to end	Day	30% 4 16% 34% 16% 1	2591
August	1st to 10th	Day	31% 5% 19% 33% 11% 1	2492
	11th to 20th	Day	36% 5% 18% 30% 11%	2384
	21st to end	Day	37% 4 17% 28% 13% 1	2376
September	1st to 10th	Day	40% 4 14% 33% 9%	2160
	11th to 20th	Day	43% 4 22% 24% 5%	2084
	21st to end	Day	51% 3 16% 24% 6%	1980
October	1st to 10th	Day	56% 3 13% 23% 6%	1854
	11th to 20th	Day	67% 3 11% 15% 4	1731
	21st to end	Day	73% 4 8% 11% 4	1782
November	1st to 10th	Day	68% 3 10% 14% 5%	1672
	11th to 20th	Day	78% 3 8% 8% 3	1578
	21st to end	Day	81% 3 8% 5% 2	1520
December	1st to 10th	Day	82% 3 8% 6% 1	1520
	11th to 20th	Day	85% 2 7% 5% 2	1915
	21st to end	Day	83% 2 5% 9% 1	2783
January	1st to 10th	Night	82% 2 7% 8% 1	2648
	11th to 20th	Night	82% 3 9% 6%	2583
	21st to end	Night	83% 4 5% 6% 1	2772
February	1st to 10th	Night	74% 4 9% 11% 2	2430
	11th to 20th	Night	69% 4 10% 14% 4	2203
	21st to end	Night	65% 3 10% 15% 6%	1776
March	1st to 10th	Night	52% 5% 11% 22% 10% 1	2160
	11th to 20th	Night	52% 3 11% 20% 12% 1	2118
	21st to end	Night	52% 4 10% 22% 11% 2	1980
April	1st to 10th	Night	58% 5% 8% 19% 10%	1800
	11th to 20th	Night	54% 4 9% 20% 11% 2	1771
	21st to end	Night	52% 4 7% 22% 14% 2	1620
May	1st to 10th	Night	52% 4 11% 19% 12% 2	1446
	11th to 20th	Night	48% 4 7% 26% 13% 1	1417
	21st to end	Night	43% 5% 12% 25% 14% 1	1552
June	1st to 10th	Night	42% 4 12% 27% 14% 2	1440
	11th to 20th	Night	44% 5% 13% 22% 15% 1	1440
	21st to end	Night	42% 4 16% 23% 14% 1	1440
July	1st to 10th	Night	32% 4 12% 34% 16% 2	1400
	11th to 20th	Night	36% 4 15% 28% 16% 1	1392
	21st to end	Night	31% 4 16% 31% 15% 2	1487
August	1st to 10th	Night	35% 4 17% 32% 9% 3	1423
	11th to 20th	Night	33% 4 16% 32% 13% 1	1512
	21st to end	Night	36% 4 15% 28% 15% 2	1980
September	1st to 10th	Night	37% 4 14% 33% 12% 1	1800
	11th to 20th	Night	43% 4 18% 30% 6%	1858
	21st to end	Night	49% 3 17% 26% 5%	1980
October	1st to 10th	Night	51% 4 13% 23% 8% 1	2105
	11th to 20th	Night	61% 4 12% 17% 5% 1	2228
	21st to end	Night	67% 3 12% 14% 4	2574
November	1st to 10th	Night	65% 4 10% 16% 6%	2406
	11th to 20th	Night	74% 3 9% 9% 5%	2598
	21st to end	Night	75% 4 10% 8% 2	2660
December	1st to 10th	Night	81% 3 8% 7% 1	2660
	11th to 20th	Night	77% 4 9% 8% 2	3281
	21st to end	Night	82% 2 7% 8% 1	4884

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	17% 15% 36% 23% 6% 2	270
	11th to 20th	Day	21% 10% 36% 25% 6% 2	252
	21st to end	Day	21% 14% 41% 20% 3	264
February	1st to 10th	Day	19% 23% 39% 17% 2	240
	11th to 20th	Day	15% 30% 31% 16% 8%	240
	21st to end	Day	20% 25% 41% 13% 1	198
March	1st to 10th	Day	14% 18% 43% 20% 4 2	240
	11th to 20th	Day	16% 19% 35% 23% 7% 1	244
	21st to end	Day	23% 13% 32% 21% 9% 2	462
April	1st to 10th	Day	22% 10% 35% 26% 5% 1	420
	11th to 20th	Day	30% 11% 26% 22% 8% 2	412
	21st to end	Day	26% 10% 29% 22% 10% 3	420
May	1st to 10th	Day	18% 12% 36% 22% 8% 3	593
	11th to 20th	Day	16% 9% 38% 24% 9% 4	625
	21st to end	Day	18% 8% 30% 29% 13% 2	679
June	1st to 10th	Day	12% 9% 34% 30% 13% 2	630
	11th to 20th	Day	17% 7% 32% 29% 11% 3	630
	21st to end	Day	15% 8% 28% 30% 15% 4	630
July	1st to 10th	Day	8% 5% 32% 35% 15% 5%	621
	11th to 20th	Day	11% 8% 31% 28% 16% 6%	618
	21st to end	Day	9% 6% 30% 33% 17% 5%	684
August	1st to 10th	Day	13% 7% 27% 33% 16% 4	626
	11th to 20th	Day	16% 5% 20% 31% 21% 7%	549
	21st to end	Day	19% 8% 23% 28% 17% 4	495
September	1st to 10th	Day	19% 6% 28% 27% 16% 5%	450
	11th to 20th	Day	17% 9% 27% 29% 17% 2	450
	21st to end	Day	24% 10% 25% 24% 13% 3	450
October	1st to 10th	Day	23% 12% 26% 23% 12% 3	324
	11th to 20th	Day	32% 19% 31% 16% 2	270
	21st to end	Day	37% 18% 30% 13% 2 1	297
November	1st to 10th	Day	25% 20% 28% 21% 5% 1	270
	11th to 20th	Day	29% 19% 37% 10% 5%	270
	21st to end	Day	25% 20% 33% 16% 5% 1	270
December	1st to 10th	Day	23% 13% 36% 20% 7% 1	270
	11th to 20th	Day	26% 20% 34% 14% 4 1	270
	21st to end	Day	26% 16% 38% 16% 3	297
January	1st to 10th	Night	17% 17% 38% 22% 5% 1	950
	11th to 20th	Night	18% 14% 38% 22% 7% 2	923
	21st to end	Night	18% 15% 35% 25% 7% 1	990
February	1st to 10th	Night	16% 18% 33% 25% 6% 1	900
	11th to 20th	Night	16% 17% 32% 23% 10% 1	808
	21st to end	Night	20% 10% 36% 27% 6%	592
March	1st to 10th	Night	14% 11% 29% 33% 10% 2	720
	11th to 20th	Night	17% 14% 31% 28% 9% 1	682
	21st to end	Night	22% 9% 23% 30% 14% 2	594
April	1st to 10th	Night	23% 7% 29% 32% 7% 2	540
	11th to 20th	Night	26% 7% 25% 30% 11% 1	533
	21st to end	Night	23% 5% 24% 32% 14% 2	540
May	1st to 10th	Night	21% 7% 27% 31% 13% 1	540
	11th to 20th	Night	19% 4 28% 33% 12% 3	531
	21st to end	Night	16% 5% 22% 36% 19% 1	584
June	1st to 10th	Night	17% 5% 18% 44% 15% 2	540
	11th to 20th	Night	15% 4 21% 44% 15% 1	540
	21st to end	Night	17% 3 20% 38% 19% 2	540
July	1st to 10th	Night	9% 4 19% 44% 22% 2	525
	11th to 20th	Night	13% 6% 26% 30% 23% 2	522
	21st to end	Night	10% 3 22% 41% 22% 3	591
August	1st to 10th	Night	11% 2 22% 40% 24% 1	537
	11th to 20th	Night	12% 3 18% 30% 31% 5%	534
	21st to end	Night	16% 5% 23% 32% 22% 2	594
September	1st to 10th	Night	17% 5% 20% 32% 22% 4	540
	11th to 20th	Night	17% 5% 25% 33% 17% 3	598
	21st to end	Night	23% 7% 24% 31% 15% 1	720
October	1st to 10th	Night	24% 10% 24% 26% 14% 1	720
	11th to 20th	Night	28% 12% 27% 23% 10%	720
	21st to end	Night	32% 11% 23% 26% 8% 1	792
November	1st to 10th	Night	25% 14% 27% 27% 7% 1	740
	11th to 20th	Night	25% 17% 29% 21% 8% 1	888
	21st to end	Night	23% 17% 31% 24% 4	950
December	1st to 10th	Night	21% 19% 34% 19% 7% 1	950
	11th to 20th	Night	19% 18% 33% 21% 9% 1	950
	21st to end	Night	27% 14% 33% 19% 6%	1045

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