Jasper
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jasper clear sky chart from 2005-11-06 to 2024-11-10.

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	14% 7% 2 7% 5% 5% 5% 4 6% 7% 39%	101020
	Night	14% 7% 2 6% 4 3 4 3 5% 7% 45%	98196
Transparency	Day	42% 6% 10% 18% 18% 7%	104665
	Night	37% 5% 11% 19% 19% 9%	102691
Seeing	Day	14% 9% 21% 25% 22% 9%	14988
	Night	16% 8% 24% 31% 19% 3	24780

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	21% 8% 3 7% 3 3 4 3 5% 6% 38%	2847
	11th to 20th	Day	21% 6% 2 5% 3 2 2 2 3 4 49%	2850
	21st to end	Day	23% 9% 3 6% 3 3 3 2 4 7% 37%	3135
February	1st to 10th	Day	19% 8% 3 7% 5% 5% 4 3 4 5% 37%	1710
	11th to 20th	Day	22% 10% 3 6% 4 3 3 2 3 5% 40%	1886
	21st to end	Day	19% 8% 3 8% 4 3 3 4 5% 5% 37%	1727
March	1st to 10th	Day	22% 12% 3 8% 5% 5% 3 3 4 5% 29%	3436
	11th to 20th	Day	19% 8% 3 7% 5% 5% 5% 4 6% 7% 31%	3480
	21st to end	Day	18% 9% 3 7% 4 4 3 3 4 5% 40%	3814
April	1st to 10th	Day	14% 7% 3 8% 5% 5% 5% 4 5% 5% 38%	2152
	11th to 20th	Day	17% 7% 3 6% 5% 5% 5% 4 5% 6% 38%	2254
	21st to end	Day	12% 6% 2 5% 5% 5% 5% 4 6% 6% 42%	2280
May	1st to 10th	Day	20% 8% 3 8% 6% 5% 5% 4 6% 7% 29%	3765
	11th to 20th	Day	13% 6% 3 7% 4 4 4 4 5% 6% 43%	3973
	21st to end	Day	11% 6% 3 7% 6% 6% 6% 5% 8% 9% 34%	4477
June	1st to 10th	Day	9% 5% 2 6% 7% 6% 6% 5% 8% 11% 35%	2470
	11th to 20th	Day	5% 5% 2 6% 6% 7% 7% 6% 9% 10% 38%	2470
	21st to end	Day	9% 6% 2 7% 6% 7% 8% 5% 7% 11% 31%	2470
July	1st to 10th	Day	9% 6% 2 8% 6% 8% 7% 6% 8% 11% 29%	4120
	11th to 20th	Day	7% 7% 4 9% 7% 8% 7% 5% 8% 10% 27%	4120
	21st to end	Day	17% 9% 3 9% 6% 6% 5% 5% 6% 8% 27%	4465
August	1st to 10th	Day	3 2 1 4 3 4 4 4 5% 9% 61%	4104
	11th to 20th	Day	3 3 1 5% 4 5% 5% 5% 7% 12% 51%	3741
	21st to end	Day	9% 5% 2 7% 6% 6% 7% 5% 8% 8% 37%	4180
September	1st to 10th	Day	9% 6% 3 6% 5% 5% 6% 4 7% 9% 40%	2265
	11th to 20th	Day	13% 6% 3 7% 6% 6% 6% 4 6% 7% 37%	2090
	21st to end	Day	10% 5% 2 5% 4 5% 4 3 6% 8% 49%	2071
October	1st to 10th	Day	7% 4 2 5% 4 4 3 3 4 5% 60%	1900
	11th to 20th	Day	10% 5% 2 4 4 4 4 3 5% 6% 53%	1900
	21st to end	Day	14% 6% 1 5% 3 3 3 2 3 5% 53%	2090
November	1st to 10th	Day	11% 6% 3 6% 5% 4 4 4 5% 6% 47%	1948
	11th to 20th	Day	12% 7% 2 6% 4 3 4 3 4 5% 50%	1900
	21st to end	Day	17% 8% 3 7% 4 4 3 2 3 5% 44%	1900
December	1st to 10th	Day	16% 8% 2 6% 4 3 4 4 5% 5% 42%	1734
	11th to 20th	Day	17% 10% 3 6% 4 4 4 3 5% 4 40%	2161
	21st to end	Day	17% 7% 3 6% 4 4 3 3 4 6% 42%	3135
January	1st to 10th	Night	17% 7% 3 6% 3 2 3 2 4 6% 47%	4108
	11th to 20th	Night	20% 7% 2 5% 3 2 2 2 2 3 50%	4120
	21st to end	Night	25% 12% 2 5% 3 3 3 2 3 6% 38%	4532
February	1st to 10th	Night	18% 8% 4 5% 4 3 3 3 5% 6% 41%	2470
	11th to 20th	Night	21% 10% 2 4 4 3 2 2 4 5% 43%	2193
	21st to end	Night	21% 8% 3 7% 3 4 3 3 4 5% 39%	1727
March	1st to 10th	Night	25% 11% 3 7% 4 4 3 3 4 6% 31%	3419
	11th to 20th	Night	21% 9% 3 7% 5% 4 4 3 5% 6% 33%	3480
	21st to end	Night	14% 7% 2 7% 5% 4 4 3 5% 6% 43%	3817
April	1st to 10th	Night	14% 6% 2 6% 5% 4 5% 3 6% 7% 42%	2025
	11th to 20th	Night	15% 7% 2 5% 3 3 4 3 4 7% 44%	1875
	21st to end	Night	13% 6% 2 5% 5% 4 4 3 4 6% 47%	1900
May	1st to 10th	Night	22% 9% 3 7% 4 4 4 4 5% 8% 30%	3130
	11th to 20th	Night	16% 6% 3 8% 4 4 3 3 4 7% 43%	2924
	21st to end	Night	11% 6% 2 6% 4 4 5% 5% 8% 11% 37%	3090
June	1st to 10th	Night	5% 4 2 5% 5% 4 4 5% 6% 9% 51%	1710
	11th to 20th	Night	4 3 1 4 4 3 4 4 7% 10% 56%	1710
	21st to end	Night	7% 4 2 5% 5% 3 4 5% 7% 11% 46%	1710
July	1st to 10th	Night	7% 5% 2 6% 5% 4 5% 5% 7% 12% 41%	2850
	11th to 20th	Night	5% 4 2 7% 5% 5% 5% 6% 9% 12% 40%	2850
	21st to end	Night	13% 8% 3 9% 5% 4 5% 4 6% 11% 33%	3098
August	1st to 10th	Night	2 1 1 2 2 2 3 3 5% 9% 70%	2836
	11th to 20th	Night	2 2 1 3 2 3 3 4 8% 12% 59%	3087
	21st to end	Night	7% 4 2 5% 5% 5% 6% 5% 8% 9% 42%	3476
September	1st to 10th	Night	7% 4 2 6% 4 5% 4 5% 7% 9% 47%	1909
	11th to 20th	Night	11% 6% 3 6% 5% 4 4 3 7% 7% 45%	2090
	21st to end	Night	9% 5% 2 6% 3 4 3 3 5% 7% 55%	2090
October	1st to 10th	Night	5% 3 1 4 4 4 5% 4 4 7% 61%	2278
	11th to 20th	Night	11% 4 2 4 3 3 3 3 5% 5% 58%	2280
	21st to end	Night	12% 5% 2 4 3 3 3 2 3 5% 58%	2508
November	1st to 10th	Night	12% 5% 3 5% 3 3 4 3 5% 6% 53%	2335
	11th to 20th	Night	11% 5% 2 5% 3 4 3 3 5% 6% 52%	2280
	21st to end	Night	16% 7% 3 6% 4 3 3 4 5% 6% 44%	2280
December	1st to 10th	Night	21% 8% 3 5% 3 3 3 3 4 5% 42%	2441
	11th to 20th	Night	16% 10% 2 6% 3 3 3 3 4 4 44%	3036
	21st to end	Night	18% 8% 2 5% 3 3 3 3 4 5% 44%	4532

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	47% 3 4 16% 22% 8%	2848
	11th to 20th	Day	40% 3 5% 17% 28% 7%	2850
	21st to end	Day	49% 3 4 16% 18% 10%	3135
February	1st to 10th	Day	51% 5% 5% 12% 18% 10%	1710
	11th to 20th	Day	49% 4 5% 14% 17% 10%	1895
	21st to end	Day	49% 5% 7% 12% 16% 11%	1727
March	1st to 10th	Day	58% 4 7% 13% 15% 5%	3436
	11th to 20th	Day	51% 5% 7% 18% 14% 5%	3480
	21st to end	Day	48% 4 7% 15% 22% 4	3814
April	1st to 10th	Day	46% 6% 6% 16% 18% 8%	2152
	11th to 20th	Day	46% 6% 9% 14% 16% 10%	2254
	21st to end	Day	39% 7% 9% 18% 22% 5%	2280
May	1st to 10th	Day	53% 7% 10% 17% 9% 4	3800
	11th to 20th	Day	40% 6% 9% 18% 24% 3	3977
	21st to end	Day	43% 9% 13% 24% 10% 1	4489
June	1st to 10th	Day	41% 9% 15% 20% 15% 1	2470
	11th to 20th	Day	39% 9% 14% 21% 15% 2	2470
	21st to end	Day	43% 10% 15% 19% 11% 1	2470
July	1st to 10th	Day	47% 7% 23% 19% 4	4056
	11th to 20th	Day	51% 6% 16% 19% 7%	4051
	21st to end	Day	54% 7% 14% 18% 6% 1	4325
August	1st to 10th	Day	20% 6% 13% 33% 26% 1	4090
	11th to 20th	Day	26% 7% 25% 36% 7% 1	3777
	21st to end	Day	43% 7% 14% 18% 17% 1	4179
September	1st to 10th	Day	39% 9% 14% 17% 15% 6%	2265
	11th to 20th	Day	45% 8% 12% 14% 15% 6%	2090
	21st to end	Day	34% 6% 11% 20% 18% 11%	2071
October	1st to 10th	Day	19% 3 6% 12% 23% 37%	3160
	11th to 20th	Day	21% 3 4 19% 31% 23%	3140
	21st to end	Day	29% 2 3 11% 41% 14%	3428
November	1st to 10th	Day	38% 5% 8% 18% 20% 10%	1948
	11th to 20th	Day	37% 4 6% 16% 27% 12%	1900
	21st to end	Day	45% 4 5% 17% 21% 8%	1900
December	1st to 10th	Day	43% 6% 9% 17% 16% 9%	1734
	11th to 20th	Day	48% 4 5% 13% 21% 9%	2159
	21st to end	Day	44% 3 6% 13% 26% 8%	3135
January	1st to 10th	Night	39% 3 7% 18% 25% 8%	4108
	11th to 20th	Night	41% 2 5% 17% 26% 8%	4120
	21st to end	Night	50% 3 5% 15% 16% 10%	4532
February	1st to 10th	Night	45% 4 7% 15% 17% 12%	2470
	11th to 20th	Night	46% 3 5% 15% 20% 10%	2194
	21st to end	Night	49% 4 6% 12% 15% 13%	1727
March	1st to 10th	Night	55% 4 7% 13% 14% 6%	3419
	11th to 20th	Night	53% 5% 8% 13% 16% 5%	3480
	21st to end	Night	41% 6% 10% 15% 23% 5%	3817
April	1st to 10th	Night	41% 6% 8% 19% 16% 10%	2025
	11th to 20th	Night	39% 5% 10% 19% 15% 12%	1875
	21st to end	Night	38% 5% 9% 18% 24% 6%	1900
May	1st to 10th	Night	52% 8% 10% 14% 12% 4	3160
	11th to 20th	Night	41% 5% 10% 18% 22% 3	2925
	21st to end	Night	38% 10% 17% 23% 10% 1	3099
June	1st to 10th	Night	29% 9% 17% 28% 16% 1	1710
	11th to 20th	Night	22% 8% 17% 33% 16% 3	1710
	21st to end	Night	30% 10% 20% 26% 13% 1	1710
July	1st to 10th	Night	35% 9% 32% 19% 4	2805
	11th to 20th	Night	34% 10% 27% 23% 7%	2796
	21st to end	Night	46% 9% 22% 18% 6%	2999
August	1st to 10th	Night	13% 5% 19% 35% 28% 1	2826
	11th to 20th	Night	17% 6% 31% 37% 7% 1	3117
	21st to end	Night	37% 10% 17% 20% 16% 2	3476
September	1st to 10th	Night	31% 11% 18% 19% 14% 7%	1909
	11th to 20th	Night	38% 7% 14% 18% 17% 7%	2090
	21st to end	Night	30% 4 11% 22% 19% 14%	2090
October	1st to 10th	Night	17% 3 6% 16% 19% 39%	3798
	11th to 20th	Night	17% 3 4 21% 30% 25%	3779
	21st to end	Night	26% 2 4 13% 38% 18%	4120
November	1st to 10th	Night	34% 4 10% 17% 23% 11%	2335
	11th to 20th	Night	33% 5% 9% 16% 25% 12%	2280
	21st to end	Night	41% 5% 6% 17% 22% 10%	2280
December	1st to 10th	Night	45% 4 7% 18% 17% 9%	2441
	11th to 20th	Night	44% 4 5% 12% 21% 14%	3037
	21st to end	Night	43% 5% 6% 15% 25% 7%	4532

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	23% 21% 36% 13% 6% 1	270
	11th to 20th	Day	30% 14% 31% 20% 4 1	270
	21st to end	Day	26% 24% 31% 17% 2	297
February	1st to 10th	Day	26% 22% 33% 15% 3 1	270
	11th to 20th	Day	38% 14% 30% 17% 1	270
	21st to end	Day	31% 30% 30% 8%	225
March	1st to 10th	Day	25% 20% 34% 15% 6%	270
	11th to 20th	Day	18% 29% 37% 12% 3 1	270
	21st to end	Day	22% 18% 42% 14% 3 1	297
April	1st to 10th	Day	17% 18% 41% 20% 4 1	332
	11th to 20th	Day	23% 19% 26% 21% 10% 1	452
	21st to end	Day	16% 13% 35% 25% 9% 2	460
May	1st to 10th	Day	20% 9% 34% 24% 13%	463
	11th to 20th	Day	13% 7% 25% 34% 17% 4	605
	21st to end	Day	9% 7% 28% 32% 19% 6%	734
June	1st to 10th	Day	9% 3 18% 31% 28% 11%	680
	11th to 20th	Day	8% 2 18% 36% 29% 7%	680
	21st to end	Day	10% 3 11% 28% 34% 15%	680
July	1st to 10th	Day	8% 1 10% 27% 39% 15%	671
	11th to 20th	Day	7% 1 6% 28% 40% 18%	668
	21st to end	Day	8% 1 5% 29% 41% 16%	739
August	1st to 10th	Day	4 1 4 25% 45% 21%	676
	11th to 20th	Day	4 1 4 19% 46% 25%	491
	21st to end	Day	12% 2 9% 22% 32% 24%	539
September	1st to 10th	Day	8% 2 9% 24% 37% 19%	475
	11th to 20th	Day	10% 2 16% 26% 32% 13%	300
	21st to end	Day	13% 4 14% 28% 30% 12%	300
October	1st to 10th	Day	7% 2 24% 40% 20% 6%	300
	11th to 20th	Day	10% 5% 22% 39% 17% 6%	300
	21st to end	Day	19% 11% 25% 26% 13% 6%	330
November	1st to 10th	Day	14% 11% 24% 31% 17% 3	297
	11th to 20th	Day	16% 13% 33% 29% 7% 1	270
	21st to end	Day	25% 16% 33% 18% 6% 2	270
December	1st to 10th	Day	18% 12% 37% 24% 6% 3	270
	11th to 20th	Day	24% 16% 37% 19% 5%	270
	21st to end	Day	24% 21% 31% 19% 3 1	297
January	1st to 10th	Night	23% 14% 30% 27% 6%	950
	11th to 20th	Night	26% 12% 28% 26% 7%	950
	21st to end	Night	25% 12% 33% 27% 4	1045
February	1st to 10th	Night	24% 14% 32% 25% 4	950
	11th to 20th	Night	28% 14% 32% 22% 4	718
	21st to end	Night	25% 18% 34% 22% 1	471
March	1st to 10th	Night	26% 11% 31% 27% 5%	570
	11th to 20th	Night	22% 12% 34% 25% 5% 1	570
	21st to end	Night	19% 10% 38% 25% 8%	627
April	1st to 10th	Night	17% 11% 41% 24% 7%	570
	11th to 20th	Night	19% 14% 30% 27% 10%	563
	21st to end	Night	17% 8% 35% 28% 11% 1	570
May	1st to 10th	Night	16% 10% 32% 32% 9%	570
	11th to 20th	Night	14% 6% 28% 37% 14% 1	561
	21st to end	Night	8% 5% 25% 36% 23% 3	617
June	1st to 10th	Night	5% 4 13% 39% 34% 5%	570
	11th to 20th	Night	5% 2 18% 46% 25% 5%	570
	21st to end	Night	7% 2 11% 34% 39% 7%	570
July	1st to 10th	Night	5% 1 7% 37% 39% 10%	555
	11th to 20th	Night	5% 1 6% 38% 41% 9%	552
	21st to end	Night	5% 1 7% 35% 46% 6%	624
August	1st to 10th	Night	4 5% 39% 44% 8%	567
	11th to 20th	Night	5% 4 38% 44% 9%	564
	21st to end	Night	10% 1 7% 29% 43% 10%	627
September	1st to 10th	Night	8% 1 7% 32% 43% 9%	570
	11th to 20th	Night	13% 9% 31% 39% 8%	570
	21st to end	Night	11% 2 10% 35% 34% 7%	570
October	1st to 10th	Night	6% 2 14% 38% 35% 4	758
	11th to 20th	Night	13% 4 23% 39% 18% 3	760
	21st to end	Night	14% 7% 25% 32% 20% 2	836
November	1st to 10th	Night	14% 6% 27% 32% 20% 2	779
	11th to 20th	Night	13% 11% 25% 38% 13%	760
	21st to end	Night	19% 10% 30% 28% 11% 1	760
December	1st to 10th	Night	26% 9% 26% 30% 9% 1	921
	11th to 20th	Night	26% 11% 29% 28% 6%	950
	21st to end	Night	24% 11% 31% 27% 6%	1045

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