Martis Creek Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Martis Creek Campground 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	2 6% 2 5% 3 3 3 3 4 6% 63%	105118
	Night	2 7% 3 5% 4 3 4 3 5% 6% 59%	102604
Transparency	Day	12% 47% 4 10% 14% 12%	104864
	Night	13% 48% 5% 10% 14% 10%	102448
Seeing	Day	14% 20% 30% 22% 11% 3	15061
	Night	11% 13% 22% 30% 19% 4	24375

By Month

Percentage Cloud Cover SW (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	2 13% 6% 8% 4 5% 4 4 7% 7% 42%	2539
	11th to 20th	Day	2 12% 4 6% 6% 5% 6% 5% 6% 6% 42%	2617
	21st to end	Day	5% 16% 5% 10% 5% 4 5% 4 5% 6% 35%	3146
February	1st to 10th	Day	3 10% 4 7% 5% 4 5% 3 6% 5% 48%	1710
	11th to 20th	Day	2 10% 4 8% 5% 3 4 4 6% 7% 47%	1835
	21st to end	Day	1 11% 5% 8% 5% 3 4 3 6% 7% 46%	1570
March	1st to 10th	Day	1 17% 10% 15% 5% 5% 5% 3 5% 6% 29%	3138
	11th to 20th	Day	2 9% 3 5% 3 3 3 3 4 6% 58%	3458
	21st to end	Day	1 15% 5% 9% 5% 5% 4 5% 5% 7% 40%	4058
April	1st to 10th	Day	3 11% 3 7% 5% 4 4 4 6% 8% 46%	2280
	11th to 20th	Day	3 10% 3 6% 4 4 4 3 5% 7% 51%	2249
	21st to end	Day	4 10% 2 5% 3 3 3 2 6% 7% 56%	2280
May	1st to 10th	Day	3 7% 1 4 2 2 2 2 3 6% 67%	3973
	11th to 20th	Day	2 5% 1 4 2 2 3 2 4 5% 70%	4341
	21st to end	Day	4 6% 2 5% 3 3 3 3 4 6% 61%	4813
June	1st to 10th	Day	4 4 2 5% 4 4 3 3 5% 8% 58%	2660
	11th to 20th	Day	2 3 1 3 2 2 3 3 3 4 75%	2660
	21st to end	Day	2 3 1 3 1 2 2 2 3 5% 77%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 2 2 89%	4420
	11th to 20th	Day	2 1 1 3 2 3 3 2 3 4 75%	4420
	21st to end	Day	1 1 1 2 1 2 2 2 3 4 81%	4669
August	1st to 10th	Day	2 1 1 3 2 2 2 2 4 5% 76%	4070
	11th to 20th	Day	1 1 1 1 1 2 2 2 3 86%	3724
	21st to end	Day	1 1 1 1 1 1 2 2 3 87%	4180
September	1st to 10th	Day	1 1 1 2 1 2 2 3 4 81%	2280
	11th to 20th	Day	2 3 1 4 2 2 2 2 4 5% 72%	2259
	21st to end	Day	3 3 1 2 2 1 2 2 4 5% 76%	2090
October	1st to 10th	Day	3 3 1 3 2 2 3 3 5% 6% 71%	3194
	11th to 20th	Day	3 4 1 3 2 2 2 2 3 4 73%	3161
	21st to end	Day	2 4 1 4 3 3 3 3 5% 7% 65%	3372
November	1st to 10th	Day	4 8% 2 5% 4 3 5% 3 4 6% 55%	1710
	11th to 20th	Day	2 7% 2 4 4 4 5% 5% 6% 9% 54%	1710
	21st to end	Day	2 7% 3 6% 5% 3 4 4 6% 8% 53%	1630
December	1st to 10th	Day	3 9% 4 7% 5% 4 4 3 7% 8% 46%	1520
	11th to 20th	Day	5% 15% 5% 8% 5% 5% 5% 4 7% 6% 33%	1928
	21st to end	Day	3 8% 3 8% 5% 5% 5% 4 8% 10% 41%	2794
January	1st to 10th	Night	2 6% 4 8% 5% 5% 5% 5% 8% 9% 43%	4406
	11th to 20th	Night	1 13% 5% 10% 5% 5% 6% 5% 6% 7% 38%	4331
	21st to end	Night	3 17% 5% 8% 6% 5% 5% 5% 6% 5% 35%	4521
February	1st to 10th	Night	2 8% 3 9% 6% 5% 5% 4 6% 6% 46%	2470
	11th to 20th	Night	1 9% 3 6% 5% 5% 5% 5% 7% 9% 46%	2232
	21st to end	Night	2 9% 4 9% 4 4 4 4 6% 8% 47%	1884
March	1st to 10th	Night	1 13% 8% 12% 5% 5% 5% 4 6% 8% 33%	3736
	11th to 20th	Night	1 11% 3 5% 4 4 3 3 5% 5% 56%	3508
	21st to end	Night	1 15% 7% 11% 6% 6% 5% 5% 6% 6% 32%	3594
April	1st to 10th	Night	3 8% 3 7% 5% 4 5% 4 7% 8% 47%	1900
	11th to 20th	Night	2 9% 3 4 4 4 4 3 5% 7% 54%	1879
	21st to end	Night	3 7% 3 4 3 3 3 3 4 7% 59%	1900
May	1st to 10th	Night	2 5% 3 4 2 2 3 3 4 5% 67%	2998
	11th to 20th	Night	1 4 1 2 2 2 2 2 4 6% 73%	2548
	21st to end	Night	3 4 2 4 2 2 3 3 4 6% 65%	2762
June	1st to 10th	Night	3 4 1 5% 3 3 4 3 4 8% 60%	1520
	11th to 20th	Night	1 2 1 2 1 3 2 2 4 4 78%	1520
	21st to end	Night	2 2 1 3 2 2 3 2 3 4 77%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 2 89%	2540
	11th to 20th	Night	3 2 1 3 3 3 2 1 3 3 76%	2540
	21st to end	Night	2 1 1 2 1 2 2 3 3 81%	2881
August	1st to 10th	Night	2 2 1 2 3 2 3 2 3 6% 74%	2869
	11th to 20th	Night	1 1 1 1 1 2 1 2 3 86%	3126
	21st to end	Night	1 1 1 1 1 1 1 3 2 86%	3498
September	1st to 10th	Night	2 1 1 1 1 1 1 1 2 4 85%	1900
	11th to 20th	Night	2 2 1 3 2 2 2 1 3 5% 77%	1920
	21st to end	Night	2 2 1 3 1 2 2 2 4 4 76%	2090
October	1st to 10th	Night	2 3 1 2 2 2 2 2 4 4 77%	3769
	11th to 20th	Night	2 2 1 3 2 2 2 1 3 5% 77%	3777
	21st to end	Night	3 5% 1 4 2 3 3 3 5% 7% 64%	4181
November	1st to 10th	Night	3 6% 2 4 4 4 4 4 6% 7% 56%	2469
	11th to 20th	Night	2 6% 2 5% 3 3 3 4 6% 9% 57%	2470
	21st to end	Night	2 6% 3 5% 5% 4 4 4 5% 7% 54%	2547
December	1st to 10th	Night	3 7% 4 7% 5% 4 5% 4 6% 7% 48%	2660
	11th to 20th	Night	4 16% 4 10% 5% 5% 5% 4 6% 9% 34%	3276
	21st to end	Night	2 10% 4 10% 7% 6% 6% 5% 6% 8% 36%	4862

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	25% 41% 9% 15% 9% 1	2539
	11th to 20th	Day	29% 45% 7% 12% 5% 2	2617
	21st to end	Day	30% 43% 7% 13% 6% 1	3146
February	1st to 10th	Day	19% 66% 4 7% 3 1	1710
	11th to 20th	Day	14% 66% 3 9% 6% 1	1845
	21st to end	Day	12% 67% 5% 9% 6% 2	1570
March	1st to 10th	Day	33% 50% 6% 3 5% 3	3138
	11th to 20th	Day	8% 43% 6% 26% 15% 2	3458
	21st to end	Day	23% 47% 10% 13% 6% 1	4058
April	1st to 10th	Day	13% 66% 5% 10% 5% 1	2280
	11th to 20th	Day	9% 67% 4 11% 8% 1	2252
	21st to end	Day	10% 66% 6% 10% 7%	2280
May	1st to 10th	Day	11% 41% 5% 22% 18% 4	3973
	11th to 20th	Day	8% 39% 5% 10% 33% 5%	4344
	21st to end	Day	9% 40% 6% 21% 22% 2	4814
June	1st to 10th	Day	5% 65% 4 9% 13% 5%	2660
	11th to 20th	Day	4 64% 3 10% 12% 7%	2660
	21st to end	Day	3 63% 1 4 11% 18%	2660
July	1st to 10th	Day	3 34% 1 3 7% 52%	4351
	11th to 20th	Day	9% 37% 3 6% 8% 38%	4345
	21st to end	Day	4 35% 2 5% 19% 35%	4522
August	1st to 10th	Day	9% 36% 2 4 14% 35%	4055
	11th to 20th	Day	3 36% 1 3 20% 37%	3760
	21st to end	Day	4 37% 1 7% 29% 23%	4179
September	1st to 10th	Day	5% 59% 1 4 16% 15%	2280
	11th to 20th	Day	7% 60% 2 10% 13% 7%	2259
	21st to end	Day	7% 59% 3 9% 14% 7%	2090
October	1st to 10th	Day	6% 36% 2 8% 26% 22%	3194
	11th to 20th	Day	10% 37% 2 7% 36% 7%	3161
	21st to end	Day	11% 38% 6% 17% 21% 7%	3372
November	1st to 10th	Day	8% 59% 4 12% 13% 5%	1710
	11th to 20th	Day	11% 61% 5% 9% 11% 3	1710
	21st to end	Day	15% 61% 5% 8% 7% 4	1630
December	1st to 10th	Day	18% 62% 5% 10% 5% 1	1520
	11th to 20th	Day	28% 52% 3 7% 7% 3	1928
	21st to end	Day	17% 41% 12% 15% 13% 2	2794
January	1st to 10th	Night	21% 43% 13% 14% 8% 1	4406
	11th to 20th	Night	30% 44% 9% 8% 7% 2	4331
	21st to end	Night	31% 45% 6% 12% 5% 1	4521
February	1st to 10th	Night	17% 68% 4 6% 4 2	2470
	11th to 20th	Night	11% 67% 4 8% 8% 2	2233
	21st to end	Night	10% 67% 6% 9% 6% 2	1884
March	1st to 10th	Night	30% 45% 6% 8% 8% 2	3736
	11th to 20th	Night	11% 44% 4 26% 14% 1	3508
	21st to end	Night	29% 49% 9% 9% 4 1	3594
April	1st to 10th	Night	12% 68% 5% 10% 6%	1900
	11th to 20th	Night	10% 67% 4 11% 7% 2	1879
	21st to end	Night	9% 66% 6% 12% 7%	1900
May	1st to 10th	Night	9% 43% 6% 22% 16% 3	2998
	11th to 20th	Night	6% 39% 4 12% 31% 7%	2548
	21st to end	Night	7% 42% 7% 26% 17% 2	2762
June	1st to 10th	Night	5% 66% 3 10% 12% 5%	1520
	11th to 20th	Night	2 65% 3 11% 12% 8%	1520
	21st to end	Night	4 62% 2 4 11% 17%	1520
July	1st to 10th	Night	3 34% 1 2 7% 52%	2500
	11th to 20th	Night	10% 35% 2 5% 7% 41%	2492
	21st to end	Night	3 35% 2 5% 21% 34%	2791
August	1st to 10th	Night	8% 36% 1 4 20% 30%	2860
	11th to 20th	Night	3 36% 1 4 24% 33%	3156
	21st to end	Night	4 36% 2 10% 27% 21%	3498
September	1st to 10th	Night	3 59% 1 4 19% 14%	1900
	11th to 20th	Night	5% 59% 2 10% 18% 5%	1920
	21st to end	Night	7% 59% 2 9% 16% 8%	2090
October	1st to 10th	Night	4 36% 2 7% 27% 25%	3769
	11th to 20th	Night	6% 37% 4 12% 34% 8%	3777
	21st to end	Night	12% 38% 5% 18% 19% 8%	4181
November	1st to 10th	Night	9% 58% 4 12% 13% 4	2469
	11th to 20th	Night	10% 60% 4 11% 11% 3	2470
	21st to end	Night	14% 61% 4 8% 7% 5%	2547
December	1st to 10th	Night	16% 62% 5% 8% 7% 2	2660
	11th to 20th	Night	23% 54% 4 6% 10% 3	3276
	21st to end	Night	22% 44% 11% 10% 11% 2	4862

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	33% 22% 23% 13% 9% 1	180
	11th to 20th	Day	28% 19% 21% 21% 10% 1	231
	21st to end	Day	16% 24% 29% 20% 8% 3	407
February	1st to 10th	Day	22% 24% 27% 17% 8% 1	370
	11th to 20th	Day	24% 24% 27% 20% 5%	448
	21st to end	Day	24% 22% 33% 17% 4 1	382
March	1st to 10th	Day	30% 29% 25% 11% 4 1	460
	11th to 20th	Day	25% 25% 24% 16% 8% 1	460
	21st to end	Day	23% 31% 27% 15% 4	506
April	1st to 10th	Day	20% 28% 27% 16% 7% 1	460
	11th to 20th	Day	24% 27% 26% 15% 6% 2	452
	21st to end	Day	17% 25% 27% 19% 10% 2	460
May	1st to 10th	Day	19% 27% 25% 21% 6% 2	463
	11th to 20th	Day	18% 23% 26% 21% 9% 3	488
	21st to end	Day	16% 18% 26% 22% 14% 4	529
June	1st to 10th	Day	12% 19% 32% 21% 12% 3	490
	11th to 20th	Day	12% 21% 36% 19% 11% 2	490
	21st to end	Day	4 15% 37% 26% 15% 3	490
July	1st to 10th	Day	3 13% 41% 27% 14% 3	486
	11th to 20th	Day	1 11% 41% 30% 14% 3	484
	21st to end	Day	2 10% 35% 32% 16% 5%	531
August	1st to 10th	Day	5% 12% 34% 29% 15% 5%	487
	11th to 20th	Day	3 14% 35% 26% 17% 5%	477
	21st to end	Day	4 12% 39% 27% 16% 3	539
September	1st to 10th	Day	3 12% 38% 29% 16% 2	490
	11th to 20th	Day	8% 17% 29% 29% 14% 2	490
	21st to end	Day	7% 16% 35% 28% 12% 2	490
October	1st to 10th	Day	8% 20% 26% 28% 15% 3	490
	11th to 20th	Day	12% 17% 22% 30% 14% 4	490
	21st to end	Day	12% 20% 29% 21% 16% 2	499
November	1st to 10th	Day	20% 16% 23% 19% 19% 4	282
	11th to 20th	Day	12% 18% 26% 22% 16% 6%	270
	21st to end	Day	13% 22% 24% 23% 15% 3	232
December	1st to 10th	Day	24% 19% 21% 18% 14% 3	180
	11th to 20th	Day	20% 27% 21% 16% 11% 5%	180
	21st to end	Day	27% 21% 25% 17% 9% 2	198
January	1st to 10th	Night	15% 16% 24% 23% 14% 7%	760
	11th to 20th	Night	16% 13% 22% 33% 12% 4	760
	21st to end	Night	11% 15% 28% 25% 17% 4	836
February	1st to 10th	Night	15% 14% 26% 27% 14% 3	760
	11th to 20th	Night	14% 15% 25% 26% 14% 5%	744
	21st to end	Night	19% 14% 22% 32% 11% 2	628
March	1st to 10th	Night	19% 20% 25% 20% 13% 3	760
	11th to 20th	Night	14% 22% 20% 22% 19% 3	760
	21st to end	Night	15% 26% 23% 23% 11% 1	836
April	1st to 10th	Night	10% 21% 28% 26% 14% 1	760
	11th to 20th	Night	14% 19% 24% 26% 13% 4	751
	21st to end	Night	10% 17% 26% 27% 18% 3	760
May	1st to 10th	Night	13% 17% 27% 25% 16% 3	656
	11th to 20th	Night	9% 11% 22% 35% 20% 2	393
	21st to end	Night	10% 9% 19% 34% 25% 3	411
June	1st to 10th	Night	6% 10% 23% 36% 23% 3	380
	11th to 20th	Night	3 11% 23% 37% 25% 1	380
	21st to end	Night	3 6% 22% 41% 25% 3	380
July	1st to 10th	Night	2 3 19% 46% 28% 2	370
	11th to 20th	Night	2 4 23% 38% 32% 1	368
	21st to end	Night	2 2 16% 39% 34% 6%	487
August	1st to 10th	Night	3 2 17% 41% 32% 4	575
	11th to 20th	Night	2 5% 21% 41% 28% 4	752
	21st to end	Night	2 5% 25% 40% 24% 3	836
September	1st to 10th	Night	2 6% 21% 39% 29% 4	760
	11th to 20th	Night	4 10% 20% 30% 30% 6%	760
	21st to end	Night	4 10% 21% 33% 23% 9%	760
October	1st to 10th	Night	7% 10% 19% 35% 23% 6%	760
	11th to 20th	Night	10% 7% 18% 37% 24% 6%	760
	21st to end	Night	10% 11% 18% 28% 22% 10%	836
November	1st to 10th	Night	14% 13% 17% 25% 24% 7%	760
	11th to 20th	Night	11% 15% 23% 29% 17% 5%	760
	21st to end	Night	12% 14% 21% 28% 19% 5%	760
December	1st to 10th	Night	17% 13% 21% 29% 15% 4	760
	11th to 20th	Night	17% 17% 24% 25% 12% 5%	760
	21st to end	Night	18% 18% 27% 24% 11% 2	836

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