Pittsburgh Space Weather Observation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pittsburgh Space Weather Observation Area clear sky chart from 2005-11-06 to 2024-11-05.

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	17% 11% 4 8% 5% 4 4 4 5% 7% 30%	101153
	Night	17% 12% 4 8% 5% 4 4 3 5% 6% 31%	97827
Transparency	Day	51% 6% 11% 20% 10% 1	104800
	Night	52% 6% 11% 19% 11% 1	102319
Seeing	Day	23% 16% 28% 20% 10% 4	14668
	Night	22% 13% 27% 25% 11% 1	24312

By Month

Percentage Cloud Cover SE (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	18% 22% 10% 12% 4 3 3 2 3 4 17%	2781
	11th to 20th	Day	13% 24% 9% 15% 7% 4 2 2 3 4 17%	2840
	21st to end	Day	26% 21% 9% 13% 6% 3 3 2 3 3 10%	3124
February	1st to 10th	Day	19% 19% 5% 12% 8% 3 4 2 3 4 21%	1710
	11th to 20th	Day	16% 14% 6% 15% 6% 4 4 3 4 6% 20%	1663
	21st to end	Day	21% 16% 4 11% 4 4 3 3 5% 6% 23%	1559
March	1st to 10th	Day	21% 12% 5% 8% 5% 4 3 3 5% 6% 28%	3435
	11th to 20th	Day	13% 13% 5% 10% 6% 4 4 3 4 5% 32%	3480
	21st to end	Day	20% 11% 3 7% 5% 3 4 3 5% 6% 31%	3815
April	1st to 10th	Day	17% 14% 3 7% 4 4 5% 4 5% 7% 30%	2191
	11th to 20th	Day	20% 11% 3 7% 5% 4 4 4 5% 6% 32%	2300
	21st to end	Day	22% 10% 3 7% 4 4 3 3 5% 6% 33%	2470
May	1st to 10th	Day	23% 9% 3 7% 5% 5% 4 3 5% 6% 28%	4082
	11th to 20th	Day	20% 9% 3 7% 5% 5% 5% 5% 6% 7% 29%	4081
	21st to end	Day	13% 6% 2 7% 4 5% 5% 5% 7% 8% 38%	4779
June	1st to 10th	Day	15% 7% 3 8% 5% 5% 5% 5% 6% 9% 32%	2660
	11th to 20th	Day	15% 6% 2 7% 6% 5% 5% 4 6% 9% 34%	2660
	21st to end	Day	15% 6% 3 6% 5% 5% 5% 4 7% 9% 36%	2660
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 5% 6% 9% 38%	4357
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 5% 7% 8% 41%	4120
	21st to end	Day	11% 6% 2 7% 6% 5% 6% 5% 6% 8% 36%	4466
August	1st to 10th	Day	15% 8% 3 9% 6% 6% 5% 5% 6% 8% 30%	4104
	11th to 20th	Day	13% 6% 3 7% 6% 6% 6% 5% 7% 9% 33%	4044
	21st to end	Day	9% 5% 2 8% 5% 5% 6% 4 7% 9% 40%	4325
September	1st to 10th	Day	16% 8% 2 5% 3 4 4 4 5% 7% 42%	2280
	11th to 20th	Day	12% 5% 3 6% 4 4 4 4 7% 7% 42%	2096
	21st to end	Day	20% 9% 3 7% 4 4 4 3 5% 6% 35%	2089
October	1st to 10th	Day	16% 7% 3 6% 4 5% 5% 4 5% 8% 38%	1900
	11th to 20th	Day	21% 9% 3 7% 5% 5% 4 4 4 5% 33%	1900
	21st to end	Day	23% 10% 3 7% 5% 3 3 4 4 6% 30%	2090
November	1st to 10th	Day	12% 10% 4 6% 5% 5% 4 3 4 7% 40%	1803
	11th to 20th	Day	18% 16% 4 7% 4 4 4 3 4 5% 30%	1567
	21st to end	Day	19% 17% 6% 9% 5% 4 3 3 5% 5% 22%	1520
December	1st to 10th	Day	20% 22% 8% 12% 5% 4 4 3 4 3 16%	1520
	11th to 20th	Day	19% 19% 7% 13% 4 4 3 3 5% 5% 18%	1910
	21st to end	Day	26% 26% 7% 9% 4 3 3 2 3 4 12%	2772
January	1st to 10th	Night	16% 23% 9% 13% 4 4 4 2 3 5% 15%	4159
	11th to 20th	Night	16% 19% 9% 16% 6% 6% 5% 3 3 3 14%	4120
	21st to end	Night	27% 18% 9% 12% 6% 3 3 2 2 3 14%	4532
February	1st to 10th	Night	19% 16% 5% 11% 8% 4 3 3 4 4 23%	2470
	11th to 20th	Night	18% 14% 5% 13% 6% 5% 4 2 5% 5% 23%	2403
	21st to end	Night	20% 13% 4 11% 6% 5% 4 3 4 4 25%	1889
March	1st to 10th	Night	23% 14% 3 7% 4 3 3 2 4 6% 31%	3418
	11th to 20th	Night	19% 13% 7% 7% 4 3 4 2 4 6% 32%	3480
	21st to end	Night	18% 10% 4 7% 5% 4 3 3 4 5% 38%	3817
April	1st to 10th	Night	18% 13% 3 7% 5% 4 4 3 4 6% 32%	1987
	11th to 20th	Night	18% 10% 3 6% 4 4 5% 4 5% 6% 35%	1844
	21st to end	Night	16% 10% 3 7% 5% 4 4 3 6% 7% 34%	1710
May	1st to 10th	Night	27% 9% 3 6% 3 4 3 4 5% 6% 28%	2813
	11th to 20th	Night	18% 10% 3 6% 5% 3 5% 3 5% 7% 35%	2812
	21st to end	Night	12% 6% 2 6% 3 3 4 4 7% 11% 41%	2772
June	1st to 10th	Night	10% 6% 2 7% 6% 4 4 4 7% 8% 43%	1520
	11th to 20th	Night	11% 6% 2 6% 5% 5% 4 4 6% 8% 43%	1520
	21st to end	Night	11% 6% 3 6% 4 4 5% 4 7% 9% 40%	1520
July	1st to 10th	Night	12% 9% 2 7% 5% 5% 4 4 5% 7% 41%	2598
	11th to 20th	Night	11% 5% 2 5% 5% 5% 5% 4 6% 9% 44%	2840
	21st to end	Night	10% 7% 3 7% 5% 5% 5% 4 6% 7% 42%	3087
August	1st to 10th	Night	14% 8% 3 8% 5% 5% 4 4 5% 7% 37%	2825
	11th to 20th	Night	14% 7% 3 7% 4 4 3 3 5% 7% 43%	2785
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 4 7% 9% 44%	3298
September	1st to 10th	Night	14% 5% 2 5% 3 4 4 3 6% 6% 48%	1900
	11th to 20th	Night	10% 4 2 5% 3 3 3 3 6% 8% 52%	2080
	21st to end	Night	19% 8% 2 7% 4 4 4 3 5% 6% 39%	2090
October	1st to 10th	Night	16% 6% 2 5% 3 4 4 3 5% 8% 44%	2280
	11th to 20th	Night	17% 8% 3 7% 4 4 4 3 5% 6% 38%	2280
	21st to end	Night	24% 9% 2 6% 4 3 4 3 5% 7% 33%	2508
November	1st to 10th	Night	13% 9% 3 6% 5% 4 3 3 5% 8% 41%	2370
	11th to 20th	Night	18% 14% 3 8% 5% 5% 5% 3 5% 6% 29%	2611
	21st to end	Night	18% 17% 4 8% 5% 4 3 3 4 6% 27%	2660
December	1st to 10th	Night	22% 18% 7% 12% 6% 4 3 3 4 4 18%	2660
	11th to 20th	Night	18% 19% 7% 11% 6% 3 4 3 4 5% 20%	3285
	21st to end	Night	25% 21% 7% 9% 6% 4 4 3 4 4 12%	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	73% 5% 8% 10% 4	2782
	11th to 20th	Day	74% 4 8% 12% 3	2840
	21st to end	Day	80% 4 7% 6% 2	3124
February	1st to 10th	Day	69% 3 9% 13% 6%	1710
	11th to 20th	Day	65% 5% 10% 14% 7%	1672
	21st to end	Day	61% 6% 10% 14% 7% 2	1559
March	1st to 10th	Day	56% 6% 10% 23% 5%	3435
	11th to 20th	Day	53% 6% 13% 20% 7% 1	3480
	21st to end	Day	52% 6% 10% 19% 12% 1	3815
April	1st to 10th	Day	53% 6% 12% 16% 12% 1	2191
	11th to 20th	Day	51% 6% 10% 17% 13% 2	2300
	21st to end	Day	52% 6% 10% 21% 10% 2	2470
May	1st to 10th	Day	55% 6% 10% 19% 8% 1	4120
	11th to 20th	Day	51% 8% 12% 19% 8% 1	4085
	21st to end	Day	40% 9% 14% 22% 12% 3	4793
June	1st to 10th	Day	46% 8% 12% 22% 11% 1	2660
	11th to 20th	Day	44% 8% 14% 20% 12% 1	2660
	21st to end	Day	43% 8% 11% 25% 12% 1	2660
July	1st to 10th	Day	41% 7% 12% 23% 14% 3	4289
	11th to 20th	Day	37% 7% 12% 27% 16%	4051
	21st to end	Day	42% 7% 13% 20% 17% 1	4324
August	1st to 10th	Day	51% 7% 12% 21% 8%	4091
	11th to 20th	Day	44% 7% 12% 27% 9% 1	4083
	21st to end	Day	39% 7% 13% 27% 13% 2	4325
September	1st to 10th	Day	40% 7% 10% 22% 17% 3	2280
	11th to 20th	Day	39% 7% 13% 24% 16% 1	2096
	21st to end	Day	49% 6% 11% 21% 12%	2089
October	1st to 10th	Day	35% 5% 11% 29% 19% 1	3160
	11th to 20th	Day	46% 5% 10% 21% 14% 4	3140
	21st to end	Day	40% 5% 13% 28% 14% 1	3428
November	1st to 10th	Day	44% 4 12% 21% 16% 2	1803
	11th to 20th	Day	56% 5% 11% 17% 9% 2	1567
	21st to end	Day	63% 5% 11% 15% 5% 1	1520
December	1st to 10th	Day	73% 5% 9% 10% 3	1520
	11th to 20th	Day	69% 5% 9% 14% 3	1906
	21st to end	Day	78% 4 9% 8% 2	2772
January	1st to 10th	Night	72% 4 10% 11% 3	4159
	11th to 20th	Night	75% 4 9% 9% 2	4120
	21st to end	Night	77% 3 7% 10% 3	4532
February	1st to 10th	Night	66% 5% 9% 16% 5%	2470
	11th to 20th	Night	64% 4 10% 16% 6%	2405
	21st to end	Night	62% 5% 8% 15% 9% 1	1889
March	1st to 10th	Night	55% 5% 10% 22% 7%	3418
	11th to 20th	Night	54% 5% 14% 20% 6% 1	3480
	21st to end	Night	47% 5% 10% 23% 13% 1	3817
April	1st to 10th	Night	53% 6% 9% 18% 12% 1	1987
	11th to 20th	Night	49% 6% 12% 16% 15% 3	1844
	21st to end	Night	47% 5% 12% 20% 12% 3	1710
May	1st to 10th	Night	55% 6% 9% 18% 10% 2	2840
	11th to 20th	Night	46% 8% 12% 23% 9% 1	2813
	21st to end	Night	33% 9% 15% 25% 15% 4	2779
June	1st to 10th	Night	37% 7% 14% 25% 16% 2	1520
	11th to 20th	Night	37% 8% 14% 23% 15% 2	1520
	21st to end	Night	38% 8% 13% 23% 16% 1	1520
July	1st to 10th	Night	42% 7% 10% 21% 18% 2	2556
	11th to 20th	Night	35% 6% 15% 27% 16% 1	2786
	21st to end	Night	40% 7% 11% 17% 23% 2	2988
August	1st to 10th	Night	46% 7% 13% 22% 12% 1	2814
	11th to 20th	Night	41% 6% 10% 30% 12% 1	2812
	21st to end	Night	35% 7% 14% 29% 13% 2	3298
September	1st to 10th	Night	35% 6% 12% 24% 19% 4	1900
	11th to 20th	Night	29% 6% 14% 27% 23% 1	2080
	21st to end	Night	46% 5% 11% 20% 16% 1	2090
October	1st to 10th	Night	36% 5% 9% 27% 23% 1	3800
	11th to 20th	Night	41% 5% 12% 22% 13% 8%	3779
	21st to end	Night	37% 4 12% 27% 18% 1	4120
November	1st to 10th	Night	42% 5% 12% 23% 14% 3	2370
	11th to 20th	Night	56% 5% 10% 18% 9% 3	2611
	21st to end	Night	58% 5% 12% 18% 5% 1	2660
December	1st to 10th	Night	69% 5% 11% 10% 4	2660
	11th to 20th	Night	67% 5% 10% 15% 3	3288
	21st to end	Night	75% 6% 9% 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	32% 28% 26% 11% 3 1	256
	11th to 20th	Day	31% 31% 27% 7% 2	270
	21st to end	Day	30% 31% 29% 8% 2	297
February	1st to 10th	Day	32% 27% 34% 7%	270
	11th to 20th	Day	35% 32% 26% 7% 1	270
	21st to end	Day	38% 28% 26% 8%	247
March	1st to 10th	Day	31% 23% 30% 12% 3	460
	11th to 20th	Day	34% 18% 34% 8% 4 1	460
	21st to end	Day	33% 21% 27% 14% 4 1	506
April	1st to 10th	Day	30% 22% 27% 14% 7% 1	460
	11th to 20th	Day	26% 20% 27% 17% 7% 3	452
	21st to end	Day	29% 19% 31% 15% 4 2	460
May	1st to 10th	Day	30% 19% 27% 18% 5% 2	463
	11th to 20th	Day	25% 13% 31% 18% 9% 3	487
	21st to end	Day	16% 9% 28% 27% 13% 6%	529
June	1st to 10th	Day	16% 13% 31% 25% 12% 3	490
	11th to 20th	Day	17% 13% 26% 28% 13% 3	490
	21st to end	Day	16% 12% 35% 24% 11% 2	490
July	1st to 10th	Day	13% 7% 22% 28% 20% 9%	485
	11th to 20th	Day	14% 6% 28% 27% 18% 7%	484
	21st to end	Day	14% 7% 26% 30% 17% 7%	532
August	1st to 10th	Day	15% 7% 23% 28% 19% 8%	486
	11th to 20th	Day	16% 6% 25% 29% 15% 9%	479
	21st to end	Day	12% 5% 24% 30% 19% 9%	539
September	1st to 10th	Day	17% 9% 22% 26% 18% 8%	490
	11th to 20th	Day	13% 4 21% 33% 18% 10%	490
	21st to end	Day	25% 11% 25% 22% 13% 3	490
October	1st to 10th	Day	16% 12% 28% 23% 18% 3	490
	11th to 20th	Day	25% 15% 30% 20% 8% 2	490
	21st to end	Day	30% 16% 29% 18% 6%	539
November	1st to 10th	Day	19% 21% 33% 16% 10% 2	377
	11th to 20th	Day	34% 21% 29% 11% 3 2	202
	21st to end	Day	24% 26% 39% 8% 2	180
December	1st to 10th	Day	34% 28% 26% 7% 3 2	180
	11th to 20th	Day	30% 25% 33% 10% 2	180
	21st to end	Day	36% 27% 28% 8% 2	198
January	1st to 10th	Night	29% 21% 35% 12% 2	760
	11th to 20th	Night	32% 20% 31% 15% 2	760
	21st to end	Night	27% 23% 31% 17% 2	836
February	1st to 10th	Night	29% 20% 29% 21% 2	760
	11th to 20th	Night	29% 22% 36% 13% 1	743
	21st to end	Night	31% 20% 31% 16% 3	628
March	1st to 10th	Night	27% 19% 32% 20% 3	760
	11th to 20th	Night	29% 18% 27% 20% 5%	760
	21st to end	Night	25% 16% 36% 19% 4 1	836
April	1st to 10th	Night	25% 18% 30% 22% 5%	760
	11th to 20th	Night	24% 15% 33% 20% 8% 1	720
	21st to end	Night	22% 11% 34% 27% 5%	570
May	1st to 10th	Night	22% 10% 26% 31% 9% 1	570
	11th to 20th	Night	19% 8% 27% 34% 10% 1	561
	21st to end	Night	11% 5% 27% 34% 21% 3	439
June	1st to 10th	Night	9% 5% 30% 38% 18%	380
	11th to 20th	Night	13% 7% 25% 39% 16%	380
	21st to end	Night	11% 5% 29% 36% 18% 1	380
July	1st to 10th	Night	9% 3 20% 41% 22% 5%	407
	11th to 20th	Night	9% 3 20% 38% 25% 5%	552
	21st to end	Night	13% 3 14% 42% 27% 2	624
August	1st to 10th	Night	13% 3 15% 42% 25% 3	567
	11th to 20th	Night	12% 4 15% 37% 27% 4	564
	21st to end	Night	11% 3 20% 34% 26% 5%	723
September	1st to 10th	Night	15% 4 24% 30% 24% 3	760
	11th to 20th	Night	12% 4 17% 35% 29% 3	760
	21st to end	Night	21% 8% 24% 26% 16% 4	760
October	1st to 10th	Night	18% 7% 25% 29% 19% 2	760
	11th to 20th	Night	21% 11% 32% 25% 8% 1	760
	21st to end	Night	27% 14% 28% 25% 6%	836
November	1st to 10th	Night	20% 13% 29% 28% 11%	760
	11th to 20th	Night	27% 18% 28% 20% 7% 1	760
	21st to end	Night	28% 18% 30% 18% 5%	760
December	1st to 10th	Night	32% 21% 27% 16% 4	760
	11th to 20th	Night	27% 24% 29% 18% 3	760
	21st to end	Night	32% 18% 30% 18% 2	836

Page generated at 2024-11-03 02:11:16. Version ac07

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